FRNSC 411 Quiz 1
What is forensic comparative science?
"Applying intelligible rules or laws of nature to the study of two physical objects, impressions, markings, or image of interest in an effort to determine whether they share a common origin"
#2 Principal Section withNormal Incidence
(A) Unpolarized light divided into TWO rays each vibrating 90° to each other(B,C) Polarized light vibrating parallel to a privileged direction experiences NO change in vibration direction. -We can thus isolate a single RI using plane polarized light!(D) Polarized light vibrating at an angle to the crystal's privileged direction is divided into TWO polarized rays each vibrating 90°to each other -B and C are analogous to rotating the polarizer 90°
Chromophoric tests
(color tests): inorganic and organic compounds - Produce color changes or light emission
Axillary hair
(i.e., armpit hair) left image is the natural distal end (i.e., uncut) and the end near the root is the right image. There tends to be a lot of cortical fusi associated with armpit hair. Next slide of axillary hair has a variable medulla from an individual with greater pigmentation. The hair is also subject to environmental damage as shown by the frayed distal end.
Hand-milling and hand-engraving
- Milling machine uses a router bit that is operated by hand and guided by a pantograph to transfer tread design to a metal (usually steel or aluminum alloy) mold blank - Differences in overall design are frequently observed (individual)
Molded processes
- Molds are used to produce soles - No cutting or trimming of the soles is required -factories may have more than one mold going at once- class
CAD-CAM process
- Same as Hand-milling and hand-engraving, except milling machine is computer controlled - Fewer differences are observed because of computer control - Example: Converse All-Stars
Cut processes
- Soles are cut and/or trimmed from pieces of soling material
Die cutting
- Use of a steel die to cut sole in a specific size/shape (just like a cookie cutter) - Can cut either cured or uncured rubber
Insect or rodent damage
- microscopically, it would appear as "chew" marks that are uneven along the shaft of the hair (insect bitemarks are shown)
Crystal Systems - Hexagonal
-120 degrees away from each other -Difference (from cubic) is we just changed one of the distances on the axes between the atoms c does not equal a a=120o c is perpendicular to a a1=a2=a3 -Uniaxial •Hexagonal •Three horizontal axes of equal length that intersect at 120 degrees •Vertical axis is longer or shorter and perpendicular to horizontal •Axes = 90o •Examples: Quartz SiO2, Calcite (CaCO3), Apatite Ca5(PO4)3(F,Cl,OH):
Combing
-A clean comb or brush is used to recover trace evidence from the hair of an individual. -The combing device and collected debris from the hair should be packaged together. -sexual assault kits -Strengths: Quick = ↓$, Collects adhering foreign particles: aerosolized particles (GSR) and dust -Limitations: Collection efficiency may be low depending on nature of hair (cleanliness and hair products)
Scraping
-A clean spatula or similar tool is used to dislodge trace evidence from an item onto a collection surface such as clean paper. -The collected debris is immediately packaged in a manner to avoid sample loss. -This technique is most often conducted within the laboratory in a controlled environment that reduces the risk of contamination or loss of the trace evidence. -Strengths: Quick = ↓$, Collects primarily surface particles, Good for larger-sized particles (fibers) -Limitations: Not very efficient at removing trace evidence, Particles may/do float in air = ↑ chance of contamination, Loose all context of how and where evidence was deposited, May lose particles during the concentration phase -Generally not recommended -must have dull edges on the side of tool
Concept of the Unit Cell
-A three dimensional box containing one or more atoms. -Basic building blocks of crystals -Describes the arrangement of atoms in the crystalline material -The relative proportions of elements in the unit cell are given by the chemical formula for the material. -Described by the lattice parameters a,b,cand angles (α,β,γ). -All crystalline materials will have one of the 14 Bravaisunit cells
Vacuum Sweeping
-A vacuum cleaner equipped with a filter trap is used to recover trace evidence from an item or area. -The filter and its contents should be immediately packaged to avoid sample loss. -The appropriate vacuum parts, filter, and trap must be changed and rigorously cleaned between each vacuuming to avoid contamination. -Consider using this method subsequent to other collection techniques as it is indiscriminate and may result in the collection of a large amount of extraneous material. -Strengths: Quick = ↓$, Good for fine dusts, -Limitations: Loose all context of how and where evidence was deposited, Removal of particles from filters, May (does) collect particles that have been previously deposited prior to crime event (removes particles from deep within article of clothing). -Not recommended for routine evidence processing
Negative - Type
-Addition of two slow directions (high indices)results in a blue color and/or pastel colors in the second and fourth quadrant. -Subtraction of fast (W) witha slow (E) direction results in subtraction - a yellow color and/ormore intense colorsIn the first andthird quadrant. -Compensator plateSlow wave direction shown by arrowHighest index direction -w>E
Three Permissible Sections
-All sections transverse the center of the indicatrix. 1. Circular section = able to measure ωonly 2. Principal Section = able to measure both ωand ε 3. Random Section = most common, able to measure ωand ε'
Preservation
-Appropriate packaging of trace evidence will vary depending on the sample type(s). -All evidence must be properly sealed in a manner to prevent tampering, loss, and contamination. -Paper folds and petri dishes are good choices for small/ loose trace evidence. -Large items (garments, sheets...) should be sealed INDIVIDIUALLY in clean unused packaging. -Wet evidence items (water, blood....) must be air dried. Care must be taken to recover trace evidence that may fall off item during the drying process. (e.g. used clean butcher paper). -Small items at a crime scene that bear visible, firmly attached trace evidence should be documented, packaged intact, and transported to the laboratory for examination. -Items at a crime scene that bear visible but easily lost trace evidence or items that are impractical to transport should be documented and the trace evidence collected by an appropriate technique.
Interference of light
-As light leaves the polarizer, the analyzer is opposite as it leaves -as it enters crystal, we see that polarized light split into to RI (one big one small). Light travels in ON and On directions. -Peak to peak is one full wavelength -Full wavelength difference between the two -as the two rays leave the crystal, resultant vector is parallel and perpendicular to analyzer direction
Consequences for Anisotropic Materials
-As we rotate the stage (between crossed polars): -There will be 4 positions of maximum brightness (45⁰off extinction) -There will be 4 positions of zero brightness: extinction points.
Glass Refractive Index Measurement (GRIM)
-Automated RI measurement -Measures RI at defined wavelengths: 488, 589, and 656 nm using photometer -Use hot stage with well-calibrated silicone oils of known dispersion. -Using phase contrast microscopy to increase Beckeline detection. -Match point determined by photometer. -Temperature coefficient of liquids>>>solids -Precision: ±0.00003 -Results typically reported to ±0.00001
Contamination and Loss
-Care must be taken to eliminate these. -Evidence examination may require multiple units. If so preplanning should be done with all parties. -Trace evidence should be collected first -Some types of evidence other than trace evidence may be more significant to a particular case and therefore should be given higher priority -Contact between items and personnel before the appropriate trace evidence has been secured should be restricted -Appropriate protective apparel (lab coats, gloves, masks) -Apparel must be changed as necessary to avoid contamination and transfer. -Handle items as little as possible -Collect, package, and seal items individually -Equipment and work surfaces must be cleaned prior to processing evidence -The examination of questioned and unknown evidence items must be conducted in different locations.
Exchange Reactions
-Cation and anion A+B- + C+D- → A+D- + C+B- • Examples: - AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) - Pb(NO3)2(aq) + KI(aq) → PbI2(s) + 2KNO3(aq) - Pb(NO3)2(aq) + K2CrO4(aq) → PbCrO4(s) + 2KNO3(aq) - Pb(NO3)2(aq) + (NH4 +)S(aq) → PbS(s) + 2NH4NO3(aq) -When mixed together the ions intermingle. determined by ksp. -solid is low ksp (precip)
Sampling Trace Evidence
-Context examinations: particle populations as a whole. Does this piece of evidence fit into the case -Target examinations: specific evidence type is of interest. EX: was a tool used to break into residence? we are looking for very specific tool -Preliminary examinations: determine what type of analysis is needed. To determine if evidence is there. -Good idea to collection trace evidence even though they may not be important at the time of collection. Best to collect everything the first time. -Best NOT to assume additional sample can be collected at a future date -Sampling should flow directly from the case questions at hand. -Significance > specificity > utility (interpretability) -Requires well-rounded criminalist(s) to make the decisions
Crystalline Materials
-Defined as "a solid whose atoms, ions, molecules are arranged in repetitive structures (lattice) that extends in all directions" -Crystallography is the study of crystal structure and formation -All particles behave like crystals except:-Amorphous substances -Glass -Unorientedpolymers
Retardation and Birefringence
-Derivation to Retardation: -Δ = c(Tn-TN) -Velocities: -Cn= t/TNand CN= t/Tn -Δ = (ct/cN- ct/Cn) -Δ = t(N-n) = Retardation -Units are nanometers -Note (N-n) =Birefringence -Unitless value
Glass Transfer, Persistence, Interpretation pt2
-Difficult to summarize given the large number of variables (glass type, tool, clothing type...) 1. It is possible to find glass on a person who has broken a window or was standing nearby. 2. The transfer process is highly variable. 3. Three to four meters is max distance for glass transfer 4. Highly variable # of fragments get transferred. Size distribution is between 0.1 and 1 mm. 5. The # of backscattered particles drops by 2x per 0.2 meters 6. Thick/ wired glasses produce more particles 7. ~50% of the backscattered fragments have original surfaces 8. Force (or pane resistance) may have an important influence on the # of particles backscattered.
Detection, Collection, and Preservation
-Each case is different! -Decide on a sequence that is appropriate for the question(s) at hand. -Record the techniques used for detection, collection, and preservation in case notes. -Record location(s) where evidence was collected. -Non-destructive!! -Detection methods include: unaided eye, oblique illumination, alternative (tunable, lasers, UV, high intensity...) light sources, low-power magnification.
Lanugo Hair
-Fetus and Newborns -Usually without medulla or pigmentation. -Very fine"downy" -Forms at 5 months of gestation -Shed after 7-8thmonth of gestation in utero (after birth)
SedimentaryRocks
-Formed by deposition of inorganic and organic material at Earth's surface and water bodies. -Deposited in layers (strata) -Important for natural resources Some formed at ocean bed --Silicates --Carbonates --Evaporates --Organic-rich Conglomerates and breccias: minerals that hold pieces of rock together. Different types of minerals EX of sedimentary rocks: sandstone, limestone, coal, calcite
Lead-alkali-silicate glass (leaded glass)
-High refractive index and dispersion -Used to manufacture crystal tableware, neon sign tubing, jewelry, etc.
Michel-Levy Chart
-Identifies minerals, crystals and fibers -Gradiating lines -has bifreingence values -has names of crystals -we can see -what can we observe -determine if my miner has birefringence -first second and third orders -interference colors (due to thickness or crystals) - how vectors are split up (because they experience different RI as they travel through isotropic materials)
Sensitivity of Becke Line Method
-In the range of ±0.002: -With experience, range can be decreased to better than ±0.002 -Accuracy can be increased by: -Closing down substage condenser diaphragm (see Becke line) -Using monochromatic illumination -Sodium D line, = 589.3 nm -Monitoring temperature (25OC) -Practice helps: -Enable recognition of useful Beckelines -Recognize that illumination intensity and the size and shape of fragments may affect examinations and/or results -Understand what colors mean in Beckeline (ie. The "Christiansen Effect") -Where Becke line disappears is where there is minimum refraction
#1 Circular Section
-In this orientation, the crystal behaves like an ISOTROPIC particle. -Vibration direction is not changed after emergence from the crystal = ZERO Retardation = Always Extinct
Interpretation: Expert Opinion
-Inference of source or probable source -Must understand the significance of both intra-and inter-sample variability -End-member conclusions: -Individualization Exclusion of a particular source -Commonly conclude: "match", "could have come from", "are consistent with", "could not exclude", among other variations -Attempts to apply statistics (frequentist vs Bayesian)
Use of Refractive Index Oils
-Liquids (typically oils) of known RI -Sets of calibrated liquids produced by R. P. CargilleLaboratories, Inc. -Liquids may be of low, moderate, or high dispersion (slope of curve for oil increases as dispersive power increases) -To accurately match RI's of a fragment and oil, immersion oils with RI's that bracket the RI of fragment will require mixing (toothpick or glass rod is acceptable) -Mixtures must be homogenous or errors will result!
Silica glass
-Made from molten quartz (costly and difficult to manufacture) -Used in specialized applications only -Low thermal expansion, great heat tolerance, transparent to wide range of wavelengths, and superior chemical and electrical resistance
Glass Transfer, Persistence, Interpretation
-Major factors affecting glass transfer and persistence: -Area of broken widow -Type and thickness of the glass -How the glass was broken -Position of the person relative to the window -Person gained entry through the window -Nature of the clothing worn by the person -Time and activities person had between breaking event and arrest -Length of time between arrest and collection of clothing -How the clothing was collected from the person -Weather during the breaking incident37
KöhlerIllumination
-Method of choice for proper microscope illumination. -Provides bright and even illumination across the field of view -Image free from glare -Adjustable image resolution and contrast
Soda-lime-silicate (soda-lime) glass
-Most common type of glass encountered -Used in many applications -Flat, container, light bulbs, stamped and pressed ware, etc.
Ideal fiber (trace evidence) searching techniques
-Must be highly efficient for removing trace evidence -A minimal number of background fibers from the recipient garment should be removed with the transferred trace evidence. -It should be possible to sample particular areas of the clothing to obtain the geographical distributions of the trace evidence -The trace evidence must be easily removable for separate mounting on microscope slides -A high speed of operation is desirable
Racial Origin
-Not always possible or meaningful -Racial Origin: Caucasian (European), Negroid (African), Mongoloid (Asian), Mixed Ancestry -Hair (typically head hair) can be used to determine ancestry, but cannot provide much more meaningful information beyond that. (although we are very much aware that there are many more ancestral groupings on the basis of DNA) Key point:There are features that are predominant in each of these ancestral groups.Mixed ancestry will typically have the phenotypically dominant traits (as opposed to recessive) presented
AbbeRefractometer
-Older version is illustrated, however, operating principle is similar -Refractometerconsists of a telescope and two refracting prisms -Liquid is layered between prisms -The telescope is rotated (prisms may also rotate) until light path exceeds the critical angle at interface between prism and liquid and the field is half light and half dark -Scale is present which is calibrated in RI -Two prisms within telescope rotate to minimize dispersion of light
Determination of RI of a Liquid
-Once a match-point detection method has been used (either Beckeline, oblique illumination, or dispersion staining), one must then determine the precise RI of the immersion oil used, particularly if two or more have been mixed -RI's of immersion oils may need to be verified (due to changes in T and/or age of oil) -RI's of liquids are easily determined with a refractometer
#1 Circular and #2 Principal Sections
-Optic Axis = Axis of Isotropy -Very important sections for determining ωand ε -Question: What would be the birefringence be for each orientation?
Examination and Analysis of Glass
-Physical comparison of fractured glass -Non-optical physical properties -Density -Thickness -Curvature -Optical physical properties -Absorption (color) -Fluorescence (float glass) -Refractive index and dispersion -Chemical properties -Elemental analysis using instrumental methods -ICP-MS, ICP-OES, or μ-XRF
Cortex Characteristics
-Pigmentation -Cellular Texture -Ovoid Bodies -Cortical Fusi -Diameter ranges Most of the features that can be used in "not exclude" or "exclude" a questioned hair are in the cortex of the hair. (Note that the other features we have mentioned need to be taken into account in addition to these cortical features).We will cover each of these features in the upcoming slides.
Medulla Characteristics
-Presence/ Absence -Style: continuous, discontinuous, interrupted, transparent -Double medulla -Medullary Index (MI): useful for differentiating human vs non-human animal -MI not useful for individualization medulla is the center area of the hair that is relatively disorganized and could contain trapped air. Microscopically, the areas of the medulla that contain trapped air spaces are dark in brightfield microscopy. There are some key features in the medulla that are very important for hair recognition: Although not shown to be consistent within an individual throughout a person's lifetime, the presence or absence of a medulla can be used as a general sorting feature (use with caution) The type of medulla can be helpful when comparing hairs (K and Q) from a relatively similar time frame Double medulla is highly uncommon so can be useful in comparisonsThe medullary index is about 1/3 of a width for a human hair, and non-human hair have a variety of medullary indices (also, animal hairs tend to have a patterned medulla that can help identify species)NOTE: the medullary index is NOT useful for individualizing human hairs -Continuous,Interrupted/fragmented, transparent
Goals of Microscopy:
-Produce a magnified image of the specimen (magnification) -Separate details in the image (resolution) -Render details visible to the detector (contrast)
Organic Sources - oGSR
-Propellant -Gun cleaning oil -Bullet lubricant/ sealers/ shellac -Some portions of the primer
Float Glass
-RI is < on the upper surface -RI is > on the float surface due to incorporation of SnO2 -UV fluorescence -In Lab Demonstration -Sheet (Heavy plate) glass -Typically float glass -manufactured: one side makes contact with pool of tin and the other does not make contact. Small amount of tin is absorbed on one float side which increases its RI. The tin causes fluorescence on one side of the glass (UV light)
Wave Normal and Ray Path in Uniaxial Crystal
-Recall: O-ray follows Snell's Law, E-ray does not. -O-ray an E-ray must vibrate 90°to each other. -Project to the center, draw the ellipse (or circle) that is 90° to the normal -The semiaxesof the ellipse are ωand ε' -Make a central section that includes normal and c-axis: this includes both E- and O-ray paths -O-ray path and normal coincide = Snell's Law -O-ray vibrates perpendicular to the central section. -E-ray vibrates within the section. Note the e-ray vibration lines are parallel to the stippled
Alteration
-Recent vs recycled hair -Insect Damage -Fungal Tunneling -PMRBs and hair degradation -Burned -Crushed
Extinction - Retardation of nλ
-Rotation of the stage by x⁰ changes the proportions of n1and N1 BUT NOT the resultant O1V1Black sample on a black background
Abbe-type Condenser(most common)
-Simple two-lens -Inexpensive -Not corrected -Good for routine work
Interpretation of Soil Evidence
-Spatial variability is not well known -Conclusions: -Could have come from same location -Excluded two samples -Inclusive -Excellent for examining "alibi samples"
Quartz Surface Textures-SEM Imaging
-Surficial etching, pitting, mechanical damage, precipitation of SiO2 -Broad categories: fluvial (river), littoral (beach), eolian(wind-blown), glacial, chemical/ diageneticalteration.
Uniaxial Indicatrix
-The edges represent RI values -The length of the radii are proportional to the RI value -All central sections are ellipses except 1 circular section. -Ellipsoid of revolution -c-axis is perpendicular to the circular section -εparallel to the c-axis -The end-member RI values are ωand ε -Light vibrating at some θto the c-axis experience intermediate RI values called ε'
Persistence Studies
-The main factors affecting the # of glass fragments found on the clothing of an individual exposed to a breaking glass window are the distanceof the person from the window and the nature of the clothing -It is likely that more fragments will be found on the footwear/ socks than on the pants of a person exposed to a breaking window then they are > 1 meter away. -As activity vigor increased the size of the retained particles decreased. -Very small proportion of fragments on one item are likely to be transferred to a second item by contact between them. -Persistence is a 2-stage process: an initial loss within the first 30-60 mins is very rapid and the second process is slower (it is possible to find glass in clothing 8 hrspost event).
In the above image of a biaxial interference figure. Select the statements that are TRUE Note: north is in the direction of the top of your screen
-The trace of the optic plane is in the SW-NE direction -the optic axes pass through the metatopes -since there are few isochromes the crystal must have low birefringence
Clipping
-Trace evidence can be recovered from fingernails by nail clipping, scraping, or both. -Fingernails may be clipped with clean scissors or clippers and packaged in clean paper. -Fingernails may be scraped with a clean implement to collect debris from under the fingernails. -Package the collected debris and the scraping device as one unit, typically in clean paper. -Commonly, fingernails from the right and left hands are packaged separately. -This does not preclude the collection of each or any nail separately from all others, such as a nail with obvious damage. -Strengths: Quick = ↓$, Collects debris that may have been deposited during physical struggle -Limitations: Commonly contains debris and skin cells for the person that was sampled
Evidence Security
-Trace evidence must be kept in secure, controlled-access areas, -Evidence must be protected from loss, damage, or contamination. -Must have continuous chain of custody from the time of evidence collection until the time the evidence is admitted into court or the case has been disposed and the evidence is no longer needed. -The security and integrity of evidence is the responsibility of all persons who may identify, collect, package, store, transport, or examine evidentiary items.
Quartz (SiO2)
-Ubiquitous mineral in the upper crust. -Forms in igneous, metamorphic, sedimentary, and hydrothermal deposits. -Commonly >99% of the mineral fraction of soils and sediments. -Typically not analyzed for K-Q comparisons or provenance assessment.
Anisotropic Materials
-Vibration directions = Preferred directions -E = ExtraordinarySnell's Law violated -O = OrdinarySnell's Law obeyed -I- vibrating within plane •= vibrating parallel to screen -We can use these vibrational propertiesto examineall transparentparticles
Washing
-Washing stain or particle with an appropriate solvent -Good for isolating "stuck" particles that would be destroyed during isolation by other methods -Dried soil, blood, oily/greasy matrices -May require subsequent filtration -Strengths: Can be very efficient, Good for dried on stains/ smear -Limitations: Requires solvent extractions or total immersion, Slow = $$$
Laminated Glass
-Windshields of all U.S. motor vehicles -Layer of plastic heat-sealed between two layers of heat-strengthened glass -Minimally tempered
RI: Intra-sample variation
-Within a single annealed float glass source is ±0.00004 ±0.00016 for tempered glass ±0.00005 -0.0003 for container glass -Typically: inter-> intra-sample variability
shearing
-bend and cut sheets of metal. two forces applied at each other but not on the same axis -shearing and grinding are different
Conoscopic interference figure
-cone of light -wider the cone of light, the more interference figure we get. -low and high birefringence crystals have different shape -High NA where theres a high magnification
Flash figure
-interference figure that is produced from a crystal who's optic axis is parallel or nearly parallel to the plane of the microscope stage -looking at one of the sections of the indicitrix -image that we see
Conoscopic observations
-looking at the cone of light that we see through the eyepiece or lens -every image point corresponds to direction in the specimen
The following types of fibers are man-made (synthetic fibers) are paired with their sign of elongation. Select the correct pairings
-nylon (+) -acetate (+) not an option -rayon(+) -polyamide (+)
Tempered Glass
-surfaces of glass heated and then cooled rapidly -Much more resistant to breakage than non-tempered glass -Must be cut and shaped prior to tempering -stronger than regular glass -when breaks, force is dispersed along entire surface and causes it to break into very small pieces -has "outside skin layer"
orthoscopic observation
-you can see specimen in image. can identify it by shape, color, cracks and defects
Variation among Test Impressions...
...will ALWAYS be present, even when produced from the same footwear.
Polyester fibers can be describes as (select all that apply):
0/2 pts -polymerization occurs via a condensation reaction between carboxylic acid and amine functional groups -man-made synthetic fibers
in the images above, the image on the right is depicts two uniaxial interface figures as it passes through two samples of anisotropic crystals. select the following statements that can be concluded from the image on the right.
0/4 pts the melatope for thinner samples is more birefringent than those from thicker samples the higher the na, the more isochromes and be collected second order red does not appear in thicker samples numerical apertures cannot exceed 0.85
Abbe's Theory of Image Formation -3 Fundamental Actions
1. Diffraction that occurs by the specimen 2. Collection of the diffracted orders by the objective. 3. Interference of these orders to produce the image (by eye or captured by an imaging system).
Glass-Manufacturing Steps
1. Raw Materials 2. Melting3. Forming (shaping) 4. Annealing (controlled cooling in lehrs) 5. Secondary Processing
Best method for fiber collection
1. visual 2. tape lift
Four Types of Sections in Biaxial Crystals
1.1 of the 3 Principal Sections 2.Semi-Random 3.Random 4.Circular
Which of the following statements are true of the biaxial indicatrix? (note: there are multiple answers)
1.5/2 pts -all them CORRECT: -The biaxial indicatrix has a positive (+) optic sign when beta is closer to alpha. -Has three principle sections -Has two optic axes -The biaxial indicatrix contains principal, random, semi-random and circular sections.
in the hartmann plot above, select the appropriate dropdown to complete true statements
1/2 pts a) the oil has a steeper slope because it has a greater index of dispersion than the grain does b) the glasses refractive index, nF, is greater than the oils refractive index, nF
in the chemical microscopy laboratory, if i am testing for the presence of calcium ion (ca2+) using iodic acid using method 1, which of the following statements best describe my positive and negative controls?
1/2 pts pos: calcium chloride and iodic acid neg: calcium chloride and water WRONG only water wrong
"Ideal" Lens Equation: Conjugate Foci
1/f = 1/p + 1/q -Where: -f= focal length -p = object distance (measured from the object to the lens) -q = image distance (measured from the image to the lens) -Magnification = m = q/p -p < q then m > 1 -Reduction = r = 1/m = p/q -p > q then m < 1
The importance of objective N.A.
10x (NA 0.4) X 10x oculars = 100x mag 40x (NA 0.95) X 2.5x oculars = 100x mag.
Somatic Origin - Not always possible
12 Different Recognized Locations: Scalp, Beard/ mustache, Pubic, Limb: Arms and Legs, Ear, Nose, Vulvar, Chest, Buttocks, Eyebrow, Eyelash, Axillary -Key points about hair that is NOT head hair:There is a lot of variability some of these non-head somatic hair. They can be identified microscopicallyWith the exception of pubic hair, they are typically NOT used for forensic comparison purposes (too much variability!)Pubic hair is used for sexual assault cases because comparison and DNA typing can provide a reliable associative value to the pubic hair as evidence in these cases
in the image above, a ray of light is passing through (in the following order) an E-W polarizer, an anisotropic crystal, and a N-S analyzer. complete the following statements.
4/6 pts ??? when the light ray enters the anisotropic crystal, it splits into fast and slow waves that are vibrating fast and slow to each other the retardation of the perpendicular ray is half lambda compared to the slow ray. the intensity of light transmitted through the analyzer is half lambda
Extinction - Retardation of (2n+1)/2λ
45°off extinction is the position of maximum brightness Colored sample on a Black Background Rotation of the stage by x⁰ changes the proportions of n1and N1AND the resultant O1V1- now vibrates at (90⁰-2x⁰) to the polarizer's privileged direction. The resultant is no longer %100 transmitted by analyzer... thus change in intensity but not hue (same N and n) Once N or n are parallel to polarizer's privileged direction, particle goes extinct.
Using images A and B above, answer the following questions
6.67/8 (a) images A and B are representations of the uniaxial indicatrix (b) Image A has a negative optic sign (c) omega (w) represents the direction of light vibrating to perpendicular. Possibly the length of the circle or vector (d) the refractive index, epsilon vibrates parallel to the optic axis
The types of chemicals found in heavy metal free primers include
? Tetracene NOT mercury ful... lead styphnate
which of the following statements best describe a positive control for microchemical testing?
? A positive control contains the test analyte and tested alongside the solution. NOT: A positive control contains the reagent test drop and tested alongside the solution.
indented marks on cartridge base and primer cap
? breech face markings -maybe ejector marks?
primer mixture located in primer cup
? centerfire ammunition
frames the field of view in the compound microscope
? field diaphragm
heavily pigmented and has a circular cross section
? jute
central tenet to Locards Exchange principal
?associative "The truth is that none can act with the intensity induced by criminal activities without leaving multiple traces of his path. . . The clues I want to speak of here are of two kinds: Sometimes the perpetrator leaves traces at a scene by their actions; sometimes, alternatively, he/she picked up on their clothes or their body traces of their location or presence"
Curvature of Field
A flat object perceived to be a curved object. -A point further away from lens will be focused closer to it: check the lens equation! -Eye can accommodate a lot, but film plane is very unforgiving.
Metamorphic Rock
A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions. -Were sedimentary or igneous or metamorphic (rare) at one point, reheated and brought back up to the surface. Structure of mineral grains have been modified. -All depends on pressure and temp. Must be greater than 150 degrees C
Abbe's Theory of Image Formation
Abbe determined that the diffracted beams of light are necessary to cause interference. That interference forms light and dark bands creating the basis to distinguish the physical features of an object.
Man-made fibers - I
Acetate(cellulose acetate) Acrylic(composed of at least 85% by weight of acrylonitrileunits) Acrylonitrile(alone and in combination with other polymers) Ginny fiber Anidex(composed of at least 40% by weight of one or more esters of a monohydric alcohol and acrylic acid) Aramid(polyamide in which at least 85% of amide linkages are attached directly to two aromatic rings) Nomex, kevlar, etc. Azlon(regenerated naturally occurring protein) Fluorocarbon (Teflon) Glass Lyocell(regenerated cellulose from solution of cellulose containing N-methylmorpholine-N-oxide (NMMO)) Imidazole(aromatic polymer with recurring imidazolegroups) Melamine (composed of at least 50% by weight of cross-linked melamine polymer) Metallic (composed of metal, plastic-coated metal, metal-coated plastic, or another core completely covered by metal) Modacrylic(composed of less than 85% but at least 35% by weight of acrylonitrileunits) Dynel, verel, etc. Novoloid(composed of at least 85% by weight of a cross-linked novolac) Nylon(polyamide in which less than 85% of the amide linkages are attached directly to two aromatic rings) Nylon 6, nylon 6.6, nylon 11, qiana, etc.
Sample Collection
Adequate, relevant, and representative. At least 30-40 taken from several parts of the scalp20-30 pubic hairs
Black-Body Radiator
All objects above absolute zero (-273 KO) will emit excess energy in the form of electromagnetic radiation. -A black-body radiator is a theoretical "perfect" radiator, emitting light over all wavelengths in the electromagnetic spectrum.The wavelengths produced by a black-body radiator depend only on the temperature. -E=HC/lambda
Uniaxial Indicatrix: 3 Permissible Sections
All sections transverse the center of the indicatrix. 1. Circular section = able to measure ωonly 2. Principal Section = able to measure both ωand ε 3. Random Section = most common, able to measure ωand ε'
Biaxial
Alpha = α =X Beta = β= Y Gamma = γ = Z Three Principal Refractive Indices/ Axes Biaxial α < α'< β< γ'<γ
Medulla
Amorphous Proteins -Susceptible to protease digestion (amount of close packaging) -Function is not known: -Heat (hair is a good insulator) -Removal of water following keratin synthesis -Maintain hair shaft diameter
Lifting - Tape or Roller
An adhesive-bearing substrate such as tape is repeatedly and firmly patted or rolled over the item causing loosely adhering trace evidence to stick to the tape. -Do not overload the tape. -The collected lifts are typically placed on a transparent backing (e.g., clear plastic sheeting, glass slides, and clear plasticor glass petri dishes). This protects against contamination and permits samples to be easily viewed and removed for further comparison. -Examined using low-moderate power magnification -Strengths:Quick = ↓$, Cover large areas, Trace evidence secured to the adhesive, The 1:1 method is good for retaining spatial orientation = good for crime scene collection, Collects primarily surface particles, Good for small particles, -Limitations: Trace evidence stuck to an adhesive, Must isolate/ cut items of interest out of the tape, Trained crime scene personnel
Hair Structure:
Analogy for a human head hair: a pencil Eraser- root of hair Length of the pencil - length of hair Graphite core - medulla Wood surrounding graphite - cortex Paint on outside of pencil - cuticle Right side of slide - SEM micrographs of the structure of hair Unorganized and air containing structure in the center of a hair cut length-wise is the medulla The overlapping scale looking structures comprise the cuticle Dense material with an elongated structure are the cortex cells that make up the cortex
The elemental features for gunshot residue particles consist of
Antimoney, barium, lead
Two common approaches to determination of suitability: analysis
Approach #1 (referred to as "of value for identification"): • Only impressions of value for individualization compared • Value for individualization indicates impression deemed to be identifiable • Impressions lacking value for individualization not further compared • Approach #2 (referred to as "of value for comparison") • Impressions of value for individualization and impressions only of value for exclusion compared
Optical Indicatrix
As light travels through it experiences different RI. -Fake colors (interference diagrams) 3 dimensional model that illustrates magnitude of the refractive index a light ray experiences as it vibrates through a material. -Model of RI and vibration direction inside a crystal -Three types: isotropic, uniaxial, and biaxial. -It is a representation of the refractive indices within a crystal. Start at center then draw vector from center that represents the value of the RI. -Isometric is a sphere because they're all the same
Calcite Experiment
As non-polarized light enters the anisotropic calcite it is actually being split into two beams -as crystal is rotated, one image stays (ordinary ray) and the other rotates (extraordinary ray). -If rotated enough, the ordinary ray disappears (its polarized.) ordinary and extraordinary ray are polarized perpendicular to one another. -can figure out the optical properties using these rays -one object but two images are formed
Refractive index
As passes from air to glass or air to water the ray of light changed direction. As light meets medium with higher RI, it causes light to deviate closer to the normal (or perpendicular). The more it refracts light, the more it causes light to change direction. Glass has Higher RI than water.
Trace Evidence
Associative value of hair Generally the most common question in forensic COMPARATIVE analyses (something you will hear over and over again in your forensic coursework) is linkage. Needs to take into account what the question is ... What is the significance of finding the victim's hair at a certain location such as a suspect's house? Depends on the relationship between the suspect and the victim. Need to ask an appropriate question to get the appropriate response! -Anything relevant to the crime Key point:The strength of associative evidence in a forensic context depends on the a priori relationships between the victim, suspect, objects and location!
Chromophoric Tests
Authoritative References: - Feigl Spot Tests I (inorganic) and II (organic) • Precipitation • Complexation • Light Generation: Luminol presumptive test for blood
scanning electron microscope can provide which of the following types of imaging signals?
Backscatter electrons, Secondary Electrons, catnodoluminescence
The majority of naturally- occurring minerals (>90%) belong to which of the following crystal system?
Biaxial
The majority of naturally-occurring minerals (>90%) belong to which of the following crystal system?
Biaxial
Melatope
Black spot that is a common center of both the black cross and the isochromes -corresponds to optic axis
Documentation
Both questioned and known trace evidence documentation whether at the scene or in the laboratory must include: -Date and time of collection -Name of person(s) collecting evidence -Descriptive listing of item(s) -Unique identifier for each item collected (e.g. item # and case #) -Location of each item (notes, sketches, measurements, photographs) -Chain of custody must be maintained.
Cartridge Case
Brass usually: copper and zinc alloy • Can also be steel, aluminum, and rarely polymer. • Contains the primer, propellant and bullet • Obturates to chamber dimensions: contains hot gases produced from the deflagration of the propellant (nitrocellulose in this case).
Bullet Components
Bullet is usually jacketed with copper but can be steel, coated in nylon (Nyclad® ). • The core is usually lead alloy. Can be tin or tungsten (armour piercing, AP). • Bullet can be full metal jacket (FMJ), soft point (SP), hollow point (HP), all lead (revolvers), wad-cutter (target).
Cortical Cells
Bundles of macrofibers600-800 microfibers Spindle Shaped ~80-100 μm long
Chromatic Aberration -Corrected
By balancing complementary shapes, dispersions and refractive indices, lens systems can be designed to remove some or all chromatic aberrations.
Crystal Systems - Tetragonal
C does not equal a C> a axes =90o -Uniaxial (one one axes is different) -Tetragonal: •Two horizontal axes of equal length (a1=a2) •Vertical axis longer or shorter •Mutually perpendicular axes (Axes = 90o -
wear patterns
CANNOT be used to individualize footwear -There is one exception...the Schallamach Pattern...
Class Characteristics aka General Rifling Characteristics (GRCs)
Caliber: Measured between opposite lands ⚫ Twist: R or L ⚫ Number or lands and grooves ⚫ Width of lands and grooves
Catagen
Catagen is towards the end of the growth cycle of the hair. A catagen hair root may or may not contain sufficient nuclear DNA for analysis. -Club root, towards end of the growth phase -amount of cells being deposited is being reduced by the hair follicle Microscopical features: somewhat roughly club-shaped root as parts of the hair growth mechanisms are turned off in the follicleNOTE: even though this hair may not have sufficient nuclear DNA for testing, mitochondrial DNA analysis is still possible
Cellulose Nitration
Cellulose sources: Cotton lintersFine, short silky fibers that are attached to the cotton seedLeftover after the ginning processWood pulp
Dispersion
Change in RI with wavelength -Quantitative Assessment: -dispersion = (nD-1)/(nF-nC)↓ value the more dispersion -nD= 589 nm -nF= 486 nm -nC= 656 nm
Sub-Class Characteristics:
Characteristics shared by a (typically smaller) group of items and are due to random occurrences outside the intent of the manufacturer.
Fiber Dyes
Chromophores-portions of molecule that absorb visible light Absorb visible light: ground state to excited state Auxophores- functional groups that cause change in color intensity-COOH-SO3H-N(CH3)2-NH2
Categorization of Textile End-Products by Usage
Clothing Women, men, and children's apparel Household use Household textiles (e.g., bedding, towels, etc.) Furnishings Upholstery Floor coverings Ropes and cordage Technical use Medical textiles Health, hygiene, ambulance, hospital, surgery, etc. Geo textiles: Tyvek Tents, tarpaulins, and awnings safety textiles Protection against heat/cold, chemicals, radiation, etc. Transport textiles For use in motor vehicles, trains, planes, etc. Industrial textiles Used for manufacture of technical products Construction textiles Used in construction of buildings, etc. Agricultural textiles
Macroscopic Features
Color (dominant factor!) Dye Band Length Shaft Characteristics Key points:Variation is important (need to consider inter- vs. intra-variability) What is the difference between inter- and intra-?
Hair Composition - Protein
Composed primarily of protein (>85% by weight: keratin and KAPs) and lipids. ~340 different proteins identified -Keratin makes up hair -high concentration of cystine in hair bc it can form disulfide bonds. Has side chain residues. Di sulfide bind created to have oxidation to create sulfide sulfide bond. Cross linkage--> strength
Becke Line & Refractive Index
Condenser completely open -Reduces contrast (nearly bleaches sample) for maximum N.A. -Condenser closed downMaximum contrast but lowest N.A. -As you get closer to the true value, the Becke lines fade. Reduce numerical aperture and you will see outline of particles more clearly (when Becke line is disappearing)
Factors Affecting Examination
Condition of skin (age of individual, disease, scars, etc.) • Deposition conditions (pressure,slippage,twisting, etc.) • Transfer media (body secretions, blood, paint, etc.) • Detection and recording techniques • Environmental conditions • Substrate
AccidentalWhorl
Consists of combination of two different types of pattern,with exception of plain arch,with two or more deltas;or pattern, which possesses some of requirements for two or more different types;or pattern,which conforms to none of previous definitions.
PlainWhorl
Consists of two deltas and at least one ridge making complete circuit,which may be spiral, oval,circular,or any variant of a circle. • An imaginary line drawn between two deltas must touch or cross at least one recurving ridge within inner pattern area.
Central Pocket Loop
Consists of two deltas and at least one ridge making complete circuit,which may be spiral,oval, circular,or any variant of a circle. An imaginary line drawn between the two deltas must not touch or cross any recurving ridge within inner pattern area.
Double Loop
Consists of two separate loop formations,with two separate and distinct sets of shoulders,and two deltas.
Which one(s) of the following steps can be taken to reduce contamination and loss of trace evidence?
Contact between items and personnel before the appropriate trace evidence has been secured should be restricted appropriate protective apparel must be changed as necessary to avoid contamination and transfer
Container Glass and Glass Fibers Usage
Container glass: Bottles and containers -Glass fibers: Continuous filament -Used in fiber optic applications and fiber-reinforced plastic composites -Non-continuous filament -Used as insulation -Three types:Fiberglass wool (glass wool), Mineral wool (slag and rock wools), Glass ceramic fibers
Dermal Papilla
Controls growth cycle Germinative(matrix) cells differentiate into various cell types. Emerge in streams: goes through different phases. Goes in cycles. Why we have hair in active stages of growth. Key point:The dermal papilla is the growth center of a hair. Growth is not continuous but comes in streams of cells. Differentiation of cells occurs here.
Tests for Copper (Cu)
Copper jacketed bullets • Potential bullet impacts • Dithiooxamide (DTO) or rubeanic acid • Produces mossy green color/ charcoal in the presence of Cu. • Sub-microgram sensitivity
Knitted Fabrics
Created by a process of intermeshing loops of yarn Two distinct knitting processes Weft knitting Loops made by each weft thread are formed substantially across width of fabric By far most common Warp knitting Loops formed with many parallel threads at same time
Woven Fabrics
Created by a process of rectangular interlacing threads - formed by weaving Warp threads Oriented lengthwise in fabric Individual warp thread is an end Weft threads Oriented widthwise in fabric Individual weft thread is a pick Weave is pattern of interlacing Three major patterns Plain weave Twill weave Satin (atlas) weave Other patterns are subtypes (derived weaves)
Factors affecting crystal growth and morphology:
Crystal structure - Concentration of reactants (if you have a slide of reagents and test drop, you take one drop and put it into the other, you create concentration gradient. Will se varying conc affecting crystal growth) - Migration of nutrients (glycerine vs water) (can control growth by controlling migration through liquid. Water or water mixed with something else) - Temperature (can keep redissolving) - Chemical reaction rate - Competing reactants - Impurities
Summary of Fiber Significance
Currently, there is no quantitative information on probability of random matches in fiber comparison However, some empirical studies have indicated probability of random matches in fiber comparison is low Thus, significance of fiber evidence in any particular case will depend upon case circumstances and must be interpreted with objectivity and good judgment
Cuticle Damage
Cuticles are easily damaged through:Environmental damageHair treatments Mechanical damage Purpose of this presentation:- yes, a lot of anatomical information about hair and its structure. As Trace Evidence scientists, we do not do histological sections, but use a compound light microscope and a comparison light microscope to look at hair identification and comparison. We will look at that in the next presentation along with the very important consideration ... conclusions and interpretation. -split ends
DisulphideBonding
Cysteine + Cysteine = Cystine (two alpha amino acids) Cross linkages = chemical and mechanical resistance -Di-sulfide bonding: important so keratin can form a stable structure
titanium dioxide in fibers
Delustrant
Soil Horizons
Deposition usually goes from oldest to youngest Zone A, Zone B, Zone C Picture
Retardation and Birefringence
Derivation to Retardation: Δ = c(Tn-TN) Velocities: Cn= t/TNand CN= t/Tn Δ = (ct/cN- ct/Cn) Δ = t(N-n) = Retardation Units are nanometers Note (N-n) =Birefringence Unitless value
GSR Analysis
Dermal Nitrate test (discredited), Atomic Absorption Spectroscopy, Nuclear Activation Analysis SEM - EDSP: Current best method
Hair Follicle
Dermal papilla: active growing center of the hair Inner Root Sheath IRS cuticle Huxley's Layer Henle Layer Outer Root Sheath: contiguous with epidermis Arrector Pili Sebaceous Gland/ Duct IRS - inner root sheath ORS - outer root sheath AP - arrector pili: allows hair to stand HS - hair shaft SG - sebaceous glandFS - follicular sheath CL - cuticle layer
Trace Evidence Examination5 steps:
Detection Isolation Identification Comparison Evaluation
The steps for trace evidence examination include the following steps in order from beginning to end of analysis:
Detection, isolation, identification, comparison, evaluation
Variation created during Manufacturing
Die cutting from pre-molded sheets - Different molds - Variations in cutting/trimming sole to size
common stabilizer in smokeless powder
Diphenylamine
These Munsell Soil-Color Charts have a hole in each of the pages, What is the purpose of the holes in these charts
Directly Compare the color of the soil sampled by viewing the soil through the hole
Primary Epidermal Ridges
Directly under surface ridges - Mirror the surface ridge
Nitroglycerin is used in the manufacture of some modern cartridge ammunition. In which of the following can it be found?
Double-base smokeless powder Triple-base smokeless powder tnt
Optic Sign
E > W Subtraction of fast (W) witha slow (E) direction results in subtraction - a yellow color and/ormore intense colorsIn the first andthird quadrant. Compensator plateSlow wave direction shown by arrowHighest index direction Addition of two slow directions (high indices)results in a blue color and/or pastel colors inthe second andfourth quadrant.123
three Principal Sections
Elliptical Sections: XY = αβ(dark shaded) YZ = βγ(light shaded) XZ = αγ(stippled)
Coarse Mineral Fractions
Examination for identification and surface texture. -Stereomicroscopy -Scanning Electron Microscopy-EDS
In the Lab
Examine for trace/biological evidence first • Make test impression(s) in a soft, malleable material - Lead - Jeweler's Wax • Examine/document the questioned item first • Need to compare items of like nature - Test impression to questioned impression - Cast of test impression to cast of questioned impression - Cast of tool to questioned impression - Cast of test mark to tool
Method IX: Hanging Drop
Examples: ammonium and sulphide ions and organic alcohols (Iodoform, organic analysis).
ACE Evaluation/Conclusions:
Exclusion • Sufficient features in disagreement to conclude two friction ridge impressions did not originate from same source • Exclusion reached only if all relevant comparable anatomical areas represented and legible in known exemplars Individualization • Sufficient features in agreement to conclude two friction ridge impressions originated from same source • No unexplainable differences between the two impressions • Likelihood impression made by different source considered a practical impossibility Inconclusive • Unable to individualize or exclude due to absence of complete and legible known prints (e.g., poor quality fingerprints and lack of comparable areas) • Corresponding features observed but not sufficient to individualize • Dissimilar features observed but not sufficient to exclude
Textile Fabrics -Categories
Fabrics composed of yarns Woven fabrics, knitted fabrics, laces, braids, nets, etc. Woven and knitted fabrics are used predominantly in manufacture of clothing and household textiles Suits, shirts, skirts, sheets, upholstery fabric, curtains, drapes, among many others Fabrics made directly from fibers Felts, nonwovens, and wads
A Bertrand lens is required to observe a conoscopic interference figure
False
Accurately measuring a footwear impression can provide information about the shoe size and height of the individual
False
During the comparison stage of the ACE-V method, only the details in agreement are considered
False
Evaluate the statement sand evaluate if all of them are true isotopic= all refractive indices are the same value. all crystal systems have 90 degree angles uniaxial= two different refractive indices, all crystal systems have 90 degree angles biaxial= three different refractive indices, all crystal systems have at least one non-90 degree angle
False
Evaluate these three statements and determine if all of them are true Isotropic= all RI are the same value, all crystal systems have 90 degree angles Uniaxial= two different RIs, all crystal systems have 90 degree angles Biaxial= three different RIs, all crystal systems have at least one non-90 degree angle
False
For biaxial crystals, there are three different refractive indicies. All crystal systems have at least one axis which is not 90 degrees from the others
False
Force was applied to a glass window. Just prior to fracturing, the side opposite the force (other side of glass) was under compression, causing it to be the initiation site for the fracture
False
Glass particles are lost at a constant rate from garments that are still being worn
False
If two plane polarized monochromatic light rays emerge from a crystal after experiencing 1.25 lambda of retardation, 0% transmission through the analyzer will occur.
False
If two plane polarized monochromatic light rays emerge from a crystal after experiencing exactly 1 lambda of retardation, 100% transmission of light through the analyzer will occur
False
In a uniaxial inicatrix, beta is a measure of either the acute of the obtuse bisectrix
False
In the manufacture of rubber soles for footwear, rubber is rolled into sheets in a process called calendaring and then inserted into injection molds as the final step to add texture to the soles.
False
On fired bullets, caliber, striations, and direction of twist are considered as class characteristics
False
Rayon is a regenerated polyamide man-made fiber
False
T or F: Virtual images formed by lenses can be recorded using digital cameras and photographic films
False
The approximate distribution of fingerprint patterns is : loops (60-65%), whorls (5-10%) and arches (35%)
False
The glass refractive index measurement (GRIM) system uses a hot stage to change the refractive index of the glass fragment to match the static refractive index of the immersion oil until it reaches a match point.
False
The line perpendicular to the vibration direction of electromagnetic radiation is called the wave normal
False
The microcrystalline test for lead using potassium iodide is Pb(NO3)(aq)+(KI)(aq)-----> PbI2(s) +2KNO3(aq) the best method for conducting this test is using Method IX, the hanging drop test
False
The most common method used for microchemical crystalline tests is method 1 from chamot & mason. it involves the adding a solid reagent crystal into a test solution
False
The unit cell is the basic building block/ unit for glass (siO2)
False
True or false? ... All the head hairs from a suspect must be collected from only one region of the scalp?
False
Volar pads are formed in utero and are only found on the tips of the fingers in developing features
False
When comparing firing pin impressions, if your questioned (Q) and cartridge casing is Winchester brand, you can exclude all other brands of known (K) cartridge casing such as Remington and UMC
False
cellulose is a man made polymer
False
In a uniaxial indicatrix, beta is a measure of either the acute or the obtuse bisectrix
False -Beta is the intermediate refractive index between alpha and gamma. The acute and obtuse bisectrix is the angle between the optic axes. They are not directly related to each other. Also, beta is the term in biaxial indicatrix, not uniaxial (omega and epsilon).
In a uniaxial indicatrix, beta is a measure of either the acute or the obtuse bisectrix
False Beta is the intermediate refractive index between alpha and gamma. The acute and obtuse bisectrix is the angle between the optic axes. They are not directly related to each other Beta is the term in a biaxial indicatrix, not uniaxial (omega and epsilon)
Addition polymers are created when monomers that contain single bonds react to form double bond linear polymers.
False The bond between the monomers are formed by addition across the bond (sp2) to single bonds (sp3 hybridization)
True or false? ... For hair comparison, need to collect just one exemplar head hair from a suspect?
False The reason to collect more than one hair and also from different regions of the scalp is to obtain a representative sampling of head hair because of the intrasample variability inherent to hair
warp orients along the length of a rope and the weft runs widthwise in a rope
False Warp and weft are terms for woven fabrics
Another name for the optic axis is the axis of anisotropy
False axis of isotropy
Another name of the optic axis of anisotropy
False axis of isotropy
Twill is a form of a knit textile
False, pattern of woven textiles
A bertrand lens is absolutely essential to observe a conoscopic interference figure in a compound polarized light microscope
False, removing an eyepiece and viewing into the light path will allow you to see the back focal plane of the objective
In polarized light microscopy, the compensators such as quartz wedge or a full wave plate, is used to directly measure the precise birefringence value
False, the compensators are used to measure the amount of retardation (wavelength, nm) not birefringence
The anagen phase of hair growth is the inactive phase
False. Anagen is the growing phase. Telogen is the inactive phase
Morphology of gun shot residue (GSR) requires spherical shapes or once-molten shapes.
False. Can be irregular and not-well defined. GSR can contain unburnt or partially burnt powder
In a uniaxial indicatrix, beta is a measure of either the acute or the obtuse bisectrix
Fasle
Soil Forming factors, Parent Material:
Few soils weather directly from the underlying rocks. More commonly, soils form in materials that have moved in from elsewhere. -Loess: If you have a mountain range, through erosion, little particles fall down and are deposited -Glacial Till: rocks are moved around -Rivers: silt, carried down to mouth of delta and enters into ocean
Textile Fibers
Fiber Cross-Sectional Shape Enhance bulk and improve the performance in end products Modification ratio MR = D/d MR > 1
Textile Production Chain
Fiber processing is first link of chain Textile goods produced in batches Differences among batches (slight or noticeable) Accumulation of chemical residues in and on fibers occurs along chain which remain in textiles after production
Textile Fibers
Fiber: Textile raw material, generally characterized by flexibility, fineness and high ratio of length to thickness Types1.Staple fibers Length is limited and relatively short 2-50 cm in length Cross-sections are 10-40 μm All natural but silk2.Filaments Fibers of infinite length (continuous filament) Man-made and silk
Fibers, Filaments, Staples, Yarns, and Threads
Fibers: strand used for spinning into yarn. Filament: continuous long fiber Staple: short length fiber Yarn: interlocked/spun (twisted) together fibers. (Also forms thread, rope, or cable). Used to make textiles. Thread: thin yarns designed for sewing/ weaving. Used to make textiles.
Papillae Pegs
Fill voids between primary and secondary epidermal ridges
What are fingerprints?
Fingerprints are the friction ridges on the palmer side of the finger which may be transferred to a surface.
Anagen- 80-95% of head hairspeed of growth is ~400 μm/ day
First stage of hair growth ... anagen phase Characterized by the production of new cells, active growth. Dermal papila is actively growing. See cluster of cells
At the Scene
First step: record in notes and PHOTOGRAPH following the routine progression series. • Check for trace evidence (esp. paint) • Wherever possible remove the surface from the scene and examine in the laboratory. • If necessary, produce a mold/ reproduction of the impression: Mikrosil, silicone-based materials, among many others.
Manufacture of Glass
Flat glass: Drawn through rollers -Float process -Glass flows onto bed of molten tin (Sn) -Vast majority of flat glass is made using this process Container glass: Some type of molding process -Pressed, blown, cast, or spun into shape of mold Glass fibers: Drawn into filaments -Created by rotary process similar to cotton candy makers -breaks into tiny pieces
Factors Affecting Transfer
Force for division and ease of divisibility of material, Force of transfer, Abundance , Persistence, Secondary Transfer, Unrelated Transfer
Development of Hair Follicle
Form in utero Continuous Process Downward invagination starts between the 2nd and 3rd month of gestation New Follicles do not form after birth Formation of bundle of cells in intermediate layer -Between the top of the skin to the dermal papilla provides lubrication for hair -One hair per hair follicle
Materials used in Glass Manufacture
Formers: Compounds that, when cooled quickly after melting, will solidify without crystallization -SiO2, B2O3, P2O5, GeO2, V2O5, As2O3, Sb2O5 -Fluxes:Used to lower melting temperature of glass (reduces cost and difficulty in manufacturing) -Na2CO3(soda ash), K2CO3(potash), Na2SO4(salt cake), Na2O, K2O, LiO, Al2O3, B2O3, Cs2O\ Stabilizers: Used to impart chemical resistance and strength to glass -CaO, MgO, Al2O3, PbO, SrO, BaO, ZnO, ZrO
Secondary Epidermal Ridges
Found between primary ridges - Under surface furrows
Physical and Chemical Weathering
Freeze/ ThawWetting/ DryingGrindingUnloadingDissolutionCarbonationHydrationRedox Rxns
Hair Ultrastructure
From right to left: The bundle on the right is a section of a hair laid horizontally along its length. The cross-section points out the different layers that comprise the cuticle.Within the cortex are bundles of cells which have lost their nuclei (you can see nuclear remnants). These cortico-cells pack up against each other and contain a LOT of keratinAs we "magnify" down into the rest of the cellular structure, we see the bundles of protein that make up the macrofibrils. Within each of them are microfibrils and the types of proteins that make up the bundles.
IMM is Hydrophilic:Rhodamine6G Staining
Fully keratinized, condensed, and dehydrated above keratogenous zone -IMM - intermacrofibrillar materials (thought to be residues from cytoplasm and nuclear remnants that surround the macrofibrils and separate them) The IMM components are susceptible to dyes such as Rhodamine 6G (red dye
Cortical Fusi
Fusiform bodies filled with gas or liquid -Cortical fusi are filled with gas or liquid and appear dark (high contrast) in the microscopical image. They tend to be very small inclusions and are more easily visible in lightly pigmented hair.
class characteristic fingerprints
General ridge pattern configuration and ridge flow level 1
Keratogenous Zone
Generation of keratin. Areas that deposit more keratin and in hair follicle there is a zone in which the keratin is actively generated.
Ion Concentrations Required for Precipitation
Given: The concentration of Ba2+ in solution is 0.01M. • What concentration of SO4 2- is required for precipitation (BaSO4) to occur? • Ksp = [Ba2+][SO4 2- ] = 1.1 x 10-10 • BaSO4 ↔ [Ba2+] (aq) + [SO4 2- ] (aq) • For precipitation to occur Q>Ksp • [SO4 2- ] = Ksp/ [Ba2+] = 1.1 x 10-10 / 0.01 = 1.1 x 10-8 M • Need slightly greater than 1.1 x 10-8 M of SO4 2- to achieve precipitation. Meaning Q>Ksp
Using the images above for light rays entering the glass (left image) and water (right image) from air (nD=1.00), which of the following statements is/are true
Glass has a higher RI than air because the light retracts towards the normal -The angle of incidence of the light ray entering the materials is 60 degrees. -The normal is perpendicular to the surface of the material?
Anagen
Good for chromosomal DNA -Actively growing -Anagen hairs end to have the follicular tag (the inside of the follicle with cells containing nuclei) so it would be suitable for nuclear DNA analysis. Microscopical features: long, non-bulbous root with a sheath of cells around the root (follicular tag). In this image, the dark central region is the medulla
Alumino-silicate glass
Greater percentage of Al added to mix -Provides greater heat tolerance than borosilicate glass and resistant to alkalis -Used in most lab glassware, cookware, etc.
Root Structure (Proximal: near scalp)
Growth Phase Dependent Anagen, Catagen, Telogen We shed 50-100 head hairs a day and is related to the hairs that naturally fall out after the telogen stage is reachedStages are anagen, catagen, and telogenNext, look at the microscopical features of the hair root
Telogen- 5-15%
Hair that has actively stopped growing is in the telogen phase.Characterized by hair easily brushed off and will fall away (shed). The root end of the hair looks like a club. NO IRS
Tectonic processes
Heat & PressureContinental collisionPressure, friction, & distortion
Skin
Heaviest body organ - - Weight ≈ 15% of body weight (≈ 20 lb or more (adults)) Area ≈ 20 ft2 • Function • Protection • Temperature regulation • Sensation • Excretion and absorption
Asian
Heavily Pigmented, Circular Cross Section, Straight Shaft
African
Heavily Pigmented, Oblate Cross Section flattened on one x-sectional axis) and as the hair grows, it tends to curl and twist (see bottom right image), Curly Shaft
Slow parallel to slow= positive optic sign
High refractive index parallel to high refractive index= positive optic sign -additive interference
Slow parallel to Slow= Positive Optic Sign
High refractive index parallel to high refractiveindex = Positive Optic Sign Blue colorwhere low retardation colors are observed Given that ε>ω
Slow parallel to Fast= Negative Optic Sign
High refractive index parallel to low refractiveindex = Negative Optic Sign Yellow color where low retardation colors are observed Subtraction of lightWatch for colors becoming more concentrated ω > ε Note the magnitudes of ωand εare drawn incorrectly, they are opposite -subtraction of light results in yellow, High RI is now perpendicular to that of the compensator -low to high order of interference colors
Two types- Depending on the relative magnitude of εand ω
If E> W then optic sign is positive If W> E then optic sign is negative Birefringence = B = n2- n1= E - W
Reaction Quotient, Q
If our test drop contains two reactants that can form an insoluble product, will it precipitate? • Q = [Ag+][Cl- ] • The difference between Ksp and Q is that the concentrations required in the reaction quotient (Q) may or may not be those at equilibrium. • If Q<Ksp, the solution is not saturated, no precip -If Q=Ksp, the solution is saturated at equilibrium -If Q>Ksp, the system is not at equilibrium, the solution is super saturated, precipitation will occur until Q=Ksp
Three Primary Rock Categories
Igneous Sedimentary Metamorphic
cools and solidifies above earths surface
Igneous rocks
Köhler Illumination -Conjugate Planes
Illumination Planes: 1.Lamp filament 2.Condenser aperture 3.Back focal plane of the objective 4.Eye point/ Ramsden disc. Image-forming Planes: 1.Field diaphragm 2.Specimen plane 3.Intermediate image plane 4.Retina of the eye/ film plane
Which of the following are true concerning a Virtual image
Image appears on the same side of the lens as the object Image cannot be projected onto a film/ sensor plane Image is upright
Refractive Index, Becke Line, and Dispersion
Immersion Method 1.Use liquid of known refractive index 2.Immerse the particle in the liquid 3.Put into optic axis of microscope for observation 4.Increase the focal length and observe 5.Adjust the immersion oil as needed
General Conclusions: Transfer and Persistence
Important to collect clothing from suspects and complainants/victims ASAP Undue significance should not be placed on exact distribution of a small number of fibers because fibers are easily lost and retransferred Failure to find fibers that match complainant's/victim's clothing does not necessarily imply a lack of contact Evidence of contact (e.g., association) found through comparison of transferred fibers will generally involve recent transfers Extremely vital to evidence integrity that proper contamination (pollution) prevention procedures are observed As time interval between offense and examination increases, fibers which do remain will be very persistent and difficult to remove; thus, efficient recovery methods must be used
Aspherical Lenses
Improved manufacturing techniques in recent years have allowed complex lens shapes to be produced inexpensively -allowing better image quality (i.e., fewer aberrations) from less complex lens systems.
Incandescence
Incandescence is the emission of electromagnetic radiation as a result of high temperature. -Note that the bar on the top is not only glowing brighter, it is also producing a different spectral distribution of light (i.e., it is more yellow).
Refractive Index (RI)
Incorrectly stated as the "bending of light" -RI = speed of light (vacuum)/speed of light (medium) -Speed of light (vacuum) = ~3.0 x 108m/s -Unit less value -Always greater than 1
Verification ACE
Independent application of ACE process utilized by subsequent examiner to support or refute conclusions of original examiner • Second examiner must be peer or more experienced • Blind verification • Contextual information withheld from examiner • Double blind verification • Contextual information withheld from examiner and supervisor • Conflict resolution occurs if original conclusion contested and not resolved through consultation
Overall Ridge Pattern Flow
Influenced by: location, shape, size of the volar pads • The volar pads appear at specific locations and times during fetal development = all humans have the same general ridge flow and crease configurations. • Believed that the ridge patterns are determined by the max curvature of the surface they develop on.
Inorganic GSR
Inorganic Sources: -Primer-derived or pGSR -Primer cup/ anvil -Cartridge case -Bullet jacket and base -Firearm chamber/ barrel -Foreign debris
Abbe's Theory of Image Formation
Interference between the 0th and higher order diffracted rays in the back focal plane of the objective generates image contrast and determines the limit of spatial resolution. -Invented the concept of Numerical Aperture -Finer detail diffracts light over larger angles, than coarser structure -Sin = λ/d -Where d is the spacing between the specimen details -decreases as λdecreases => shorter λfor better resolution -The more orders collected, the sharper and better resolved the specimen
Circular Section - ConoscopicView
Interference figureBack Focal Plane of the objective Vibration directions of E and O rays in interference figure
Scanning Electron Microscopy
Interwoven elliptical void spaces that are parallel to the hair shaft - result of IMM degradation within the cortex
ACE Analysis
Is it a fingerprint? • Assessment of impression to determine value based on Level 1, 2, and 3 detail • Determine if impression is suitable for comparison • If not suitable, examination stops at analysis phase • If impression suitable, analysis further indicates features and tolerances for comparison • Assessment of tolerances assigned to impressions (unknown and known) • Tolerance = allowance of acceptable variation in friction ridge features during comparison
Formation of Biaxial Isogyres-Biot-Fresnel Rule
Isogyres: sites of extinction. Assume E-W polarizer:Only light vibrating E-W will emerge from crystal but is blocked by N-S analyzer. Absence of light vibrating N-S
Extinction - Retardation of 0λ
Isotropic material appears dark, or extinct, between crossed polarizers because material does not alter direction of polarization; thus, all transmitted light through material is absorbed by analyzer resulting in a dark image of material -Even when stage is rotated completely (360 ̊), material remains dark
In the m=images above, the image on the right depicts two unixial interface figures as it passes through two samples of anisotropic crystals. select the following statements that can be concluded from the image on the right.
It IS NOT (0/4 pts): The melatope for thinner samples is more birefringent than those from thicker samples. or: the higher the numerical aperture (N.A) the more isochrones can be collected. or: second order red does not appear in thicker samples. Or: numerical apertures cannot exceed 0.85 Possibly: The thicker the sample specimen, the more isochromes can be observed
In the pie chart above for the trace evidence remove from the victim's body, this chart tells us that
It takes time and effort to recover the small quantity of associative evidence between the victim and suspect
2V = Acute Optic Axial Angle
Just like Uniaxial crystals, there are two flavors of biaxial crystals: + and -Depends on relative magnitude of β2Vx+ 2Vz= 180° + = βcloser to α, A.B. is γ - = βcloser to γ, A.B. is α
Keratin Synthesis
Keratin is synthesized in large quantities and will occupy most of the cellular (cytosol) of the cortical cells. -loses nucleus at end of growth
Opinion - MicroscopicalExamination
Key points:Hair comparison results opinions offered do NOT individualize the hair to a source!!!With current technology, non-exclusion ("could have come from") help to reduce the backlog on nucDNA and mtDNA analysis because it provides a microscopical assessment of "yes, there is a follicular tag for nucDNA analysis" or "there is no follicular tag so you have a better chance of getting some information via mtDNA analysis"
Comparison Microscopy
Key points:Lighting background must be the same! Why? ... pigmentation comparisonMagnification must be the same! Why? ... diameter comparisonThe hair scales must be pointed in the same direction! Why? ... personal preference
Pubic hair
Left image shows how pubic hair can exhibit "kinks" in the hair shaft which give rise to the random curly shape of most pubic hair. Medulla can be variable.
Principal Section
Light is divided into two vibration directions, each parallel to a "full" Principal RI value (α, β, γ). Obey Snell's Law
European
Light pigmentation, Oval Cross Section, Straight Shaft
Circular Section
Light travel up one of the two optic axes. Light experiences ONLY 1 RI value: β. Crystal behaves like an isotropic material. Two of these directions exist.... Thus called Biaxial.
Possible reasons for finding only a small number of fibers
Long time interval between contact/transfer and examination of garment Fibers arrived on garments via redistribution Secondary, or subsequent, transfer occurred Inefficient recovery method Donor was a poor "shedder" Recipient was a poor "receiver"
Sources of Individual Characteristics
Manufacturing Imperfections • Use/Abuse • Decay/Corrosion
What is a Toolmark?
Marks from "any manner of cut, pinch, snip, score, notch, gash, hack, slash, nick, impression, depression, indentation, dent, hole, serration, dimple, hollow, bump, burrow, tunnel, punch, puncture, bend, or striation" • Tools can leave striations (slide), impressions (compression), or both. • Class and Individualizing characteristics • Subclass characteristics: striations, flaws, and imperfections that are unique to that set of manufactured tools
Polymer Fiber Production (synthetic and regenerated cellulose)
Melt Spinning Thermoplastics, molten material forced through spinneret Dry Spinning Polymer dissolved in solvent, forced through spinneret, solvent evaporates leaving polymer filament Wet Spinning Polymer dissolved in aqueous/ organic solvent, forced through spinneret that is immersed in bath of coagulating chemicals, polymer precipitates from the bath. Following extrusion, filaments are stretched/ drawn to mechanically orient the molecular chains along the longitudinal fiber axis
p-GSR
Metal = brass, copper, nickel-plated copper/brass, cupronickel, and zinc-coated steel
interference chart
Michel-Levy
Cuticle Characteristics- Thickness, condition, and pigmentation
Microscopical observations for the cuticle are helpful, but sometime obscured by the pigmentation of the hair. The cuticle thickness can vary significantly between individuals of different races (genetic variation ... more about ancestry later in the presentation)
(a) Describe the optical indicatrix for an isotropic material. (b) Describe the optical indicatrix for a uniaxial material. (In your explanation for isotropic and uniaxial indicatrices, include: What do the direction and vectors represent?, If relevant, what are some key cross-sections within the indicatrices?, If relevant, are there different forms of the indicatrices?, If relevant, are there axes that are important?) (c) Why is the optical indicatrix a useful conceptual tool for optical crystallography?
Midterm
Inner Root Sheath
Might be seen in hair that has been pulled out of a hair follicle. Holds hair follicle in place. Sticky between IRS and HS
Four components of soil:
Mineral material Organic material Air Water
Metamorphic Minerals and rocks
Minerals: Sillimanite Kyanite Andalusite Garnet Mica (biotite and muscoviteChlorite Rocks: Gneiss Slate Marble Schist Quartzite
Interference of light
Monochromatic illumination: two parent waves vibrating 90 degrees to each other. Has the same wave lengths -Amplitude of waves can be added and the resultant wave will be traveling in a different wave of polarization. -additive: intensity of light that results is larger (scalar value). Direction of resultant wave is different than both parent waves.
Borosilicate glass
More than 5% boric oxide added to mix -Provides low thermal expansion and better resistance to acid corrosion -Used in some lab glassware, cookware, etc.
Spinnerets
Morphology controls cross-sectional shape
Weave -Tufting
Most common method to make floor coverings (carpet) 32Primary backing is commonly polypropyleneAcrylic latex adhesiveJute secondary backing
Man-made fibers
Multifilament- very fine continuous fibers, <50 μm Polyamide (Nylon) Polyester Polypropylene (inexpensive) Monofilament - course fibers Polyethylene Polypropylene Fibrillated and roll embossed film Extruded as a tape, oriented by heat treatment Polypropylene
Fiber-Forming Polymers
Must have following characteristics regardless of chemical composition: Linear molecular chains with some degree of extension or orientation to fiber axis which yields a structure stronger longitudinally than transversely High molecular weight which imparts a high melting point and low solubility in most solvents Molecular chains should be flexible; thus, providing extensibility* and drape (particularly in apparel)* The extent of the ability of a textile to stretch when a tensile force is applied to it.
Resolution-Numerical Aperture
N.A. is a measure of the light-gathering ability of a lens. -Arguably the most important quality metric of a lens/system. -The higher the N.A. the better. -Commonly ranges from 0.1 to 1.4 -Mathematical Expression: -NA = n(sinAA/2) -NA = n(sin μ)
The first significant research conducted on fiber transfer persistence was conducted by which researcher(s) in 1975
NOT: Edmund Locard It is: Robertson and Greive
The above images are of a man-made fiber between cross-polarizers. The image on the right is the same, but with a full-wave compensator inserted (With the slow wave in the NE-SW direction. The fiber exhibits
NOT: moderate LOw
Polyester fibers can be described as (select all that apply):
NOT: polymerization occurs via a condensation reaction between carboxylic acid and amine functional groups IT IS: man-made synthetic fibers IT DOES: occur via condensation alcohol functional Possibly: boats in the 18th century
Through which section of a biaxial indicatrix will you be viewing down one of the optic axes?
NOT: the principal sections possibly circular sections
Catagen- few %
Near the end of the growth phase is the catagen phase (least percentage of hair is in this phase) Characterized by the follicle slowing down the production of new cells, less differentiation, and remainder of hair continues to move out of follicle. -build up of collegen.
Twist level
Number of twists per unit of length
Resolution Calculations -Radius of the Airy Disk!
Numerical aperture is very important -Wavelength of illumination -R = 0.61λ/NA -R = 1.22λ/(NAobj+ NAcond)
The following are synthetic (man-made) fibers: acrylic, aramid, nylon, lyocell, olefin, and ployester. select TWO of the only and provide a definition, description of them.
Nylon- nylons are light, elastic, synthetic polymers that can form yarn or stockings. It is a Polyamide in which less that 85% of the amide linkages are attached directly to two aromatic rings Polyester- also a synthetic polymer but it is formed using PTA, unlike nylon it is made more for jackets or sheets. It is composed of at least 85% by weight of an ester of a substitutes aromatic carboxylic acid
Polarized Light
One vibration direction perpendicular to propagation direction = plane polarized light -Required for examination of anisotropic particles -Far more complicated than usually depicted
Indicatrix and Crystallographic Axes
Orthorhombic: three RI are parallel to the three crystallographic axes. (In NO order). Monoclinic: one RI is parallel to the b axis. The other two are not. Triclinic: the RI values only coincide with the crystallographic axes by chance.
Ovoid Bodies
Oval shaped pigment bodies in the cortex -cortical features that you can easily see in the microscopical image. They are distinct from the overall pigmentation because they have a higher degree of pigmentation. They arise from their precursor melanocytes that produced more pigmentation than the average amount from the other melanocytes. The ovoid shape has the long axis in the same direction as the length of the hair.
Soil Forming process, time:
Over time, soils exhibit features that reflect the other forming factors. Soil formation processes are continuous.
Pre-Molded Oversize and "Exact" Size Soles
Oversize - Soles cut from pre-molded sheets that are compression molded and cured which may contain several sole impressions oriented in opposite directions - Soles molded individually that are larger and cut down to size • "Exact" size - Soles individually molded to the "exact" size desired and require only minor trimming 3
Volar skin surfaces:
Palms, fingerprints, soles of feet • Increase grip, fine textural perception -increase grip and sensitivity
In the above image of a hair follicle, please provide a name for each part of the follicle indicated:
Part A is hair shaft Part B is sebaceous gland Part C is arrector pili Part D is dermal papilla The purpose/ function pertaining to part B is to secrete oily substance
This is an image is a representation of hair shaft of a human head hair viewed through a microscope. Name each of the parts, K, L,N,P, and R. (NOTE that R are the darker colored features, and N are the lighter colored features.)
Part K is: cortex Part L is: medulla Part N is: cortical fusi Part P is cuticle Part R is pigment granules
This question is about interpretation of a p-GSR analysis If your analysis showed that about 20+ particles with three components (Ba, Sb, Pb) on the palm and back of hand of the suspect, which of the following statements would you state in the report results and interpretation section?
Person was in the vicinity of a discharging firearm Person handled a firearm after it was discharged person fired a gun person touched a surface contaminated with GSR
For the formation of soil, processes such as freeze/thaw cycles, grinding of rocks, dissolution of minerals, and hydration reactions are considered what type of process?
Physical and chemical weathering
Pigmentation -eumelanin (black/ brown) and phaeomelanin(reddish yellow)
Pigments in hair are small bodies of densely packed bodies of melanin Eumelanin imparts darker colors (black/brown) Phaeomelanin is lighter in color (reddish yellow) The more pigment bodies there are, the more like that color the hair will appear macroscopically -More pigment bodies= more likely hair will take on that color of the pigment
Soil forming Factors, Biological Factors:
Plants, animals, micro-organisms, and humans affect soil formation. Animals and micro-organisms mix soils and form burrows and pores. Plant roots open channels in the soils.
differential absorption of color
Pleochroism
What does the optic sign tell us?
Positive (+) or Negative (-) If Positive: γis the Acute Bisectrix(αis obtuse bisectrix) Βis closer to α If Negative: αis the Acute Bisectrix(γis obtuse bisectrix) Βis closer to γ
In the images above, the left image is the interface figure of a uniaxial crystal under crossed polars. The right image is the same crystal under the crossed polars with a full wave compensator (550nm). The slow wave of the full wave compensator is vibrating in the SW-NE direction (withNorth towards the top of your screen). What is the optic sign of the unixial crystal?
Positive optic sign
The above images are of a man made fiber between cross-polarizers. The image on the right is the same, but with a full-wave compensator inserted (with the slow wave in the NE-SW direction). The fiber exhibits
Positive sign of elongation
Potassium Ferrocyanide - Fe+3
Produces Prussian Blue (pigment) • Fe+3 + K4Fe(CN)6 → Fe4(Fe(CN)6)2,3 • Spot test or micro-crystal via Method III
Ray Propagation (Random Section)
Project wave normal to the center, extend outward to produce ellipse (or circle). STIPPLED SECTION Major and minor semi-axes are the RI values light experiences. Each vibration direction and wave normal define a plane (2 shaded ellipses). These are 90° to each other. The ray path, wave normal, and vibration direction always lie within the same plane.
Real Image:
Projected on opposite side of object -appears inverted -Can be captured on a film/sensor array.
Conoscopic View
Projecting light through the crystal leads to interference of light - Uniaxial Crystals E = Epsilon E' = >W but < E W = Omega
Conoscopic View
Projecting light through the crystal leads to interference of light E = Epsilon E' = >W but < E W = Omega
Three possible conclusions
Questioned fiber(s) consistent with having originated from comparison (known) sample Questioned fiber(s) not consistent with having originated from comparison (known) sample Inconclusive determination
Semi-Random Section
R1: Note the wave normal and ray propagation direction coincide: mimics the O-ray in uniaxial, follows Snell's Law. R2: Ray and normal do not coincide, mimics the E-ray, does not obey Snell's Law. Experiences a Principal RI (R1) and a prime value RI (R2).
Random Section
R1and R2: Ray path and wave normal do not coincide. Both do not obey Snell's Law. Both rays behave as E-rays. Experiences ε' and γ'
you are asked to assess these textile damage and if a bullet passing through them could have caused the damage
RI could have been caused by a bullet passing through a textile of synthetic fibers possibly: li could have been made caused from a bullet passing through a textile made from vegetable (plant fiber)
Spherical
Rays of light that are off the optical axis of the lens are focused at different locations. -Points closer to the periphery of the lens have short focal lengths -Coverglass correction
Intrusion of magma
Re-meltingof protolith New elements added
Method I (Most Common)
Reactant Concentration Gradient: Hoping to find location where Q > Ksp -possibly different crystal growth due to different concentration
Method III
Reagent solution drawn over dried test solution crust • Example: Potassium with Tartrate -reagent into test solution. draw liquid into dry crust. looking for different crystal formtion
Metamorphic Minerals
Recrystallize calcite in limestone and chalk making large crystals called marble. •High temperatures and pressures allow atoms & ions to migrate in solid form •Pressures force crystals into (liquid and solid) solution and begin migrating All this leads to new minerals
Immersion Methods
Relief -Indication of degree of similarity of RI's of oil and fragment -Large difference between noil and nfragment creates higher relief and vice versa
Chromatic
Remember dispersion? -Different wavelengths have different RIs -The focus for one wavelength can be slightly different then another wavelength.
Vellus
Replace lanugo just before birth Usually without medulla or pigmentation. Very fine"downy" "fuzz" Spread ~uniformly over body -short or unnoticed, uncolored usually. arms, cheeks -not much forensic significance
Arch (5%
Ridges - Enter from one side Rise up Exit opposite side - - • Subtypes - - Plain Tented
Loop (60-65%)
Ridges - Enter on one side Recurve Exit same side as enter - - • Subtypes - Radial - Flows toward radius bone - Ulnar - Flows toward ulna bone
Whorl (30-35%)
Ridges - Generally circular Subtypes - Plain whorl Central pocket loop Double loop Accidental whorl
Cartridge Anatomy
Rim fire versus Center fire • Cartridge Case • Primer • Propellant • Bullet
Nylon (Polyamide) Manufacture
Runtime 4:51 First man-made fiber, 1939 Trade Names: Nylon 6.6: Antron, Rhodiastar, TACTEL, and Ultron Nylon 6: Perlon, Enkalon, Patina, Ansa, and Zeftron
Polyester Production
Runtime 4:58, melt spun77% of the world's synthetic fiber production in 2004. Trade names: Dacron, Terylene, Fortel, Terigal, Trevira, Grilene, Diolen, and Tergal
Cortex
SEM micrographs of bundles of cortical cells with the cellular componentsCircled part in the image is a cortical cell with microfilaments in a bundle (macrofilament)
Qualitative Analysis
Safety: toxins, explosives, drugs • Microgram to submicrogram quantities of analyte • Elemental/ compound identification • Molecular species identification: borates, organic acids, anions of nitrogen, phosphorus, Sulphur, halogen and chromium groups. • Oxidation state specific: Fe2+ vs Fe3+ (potassium thiocyanate and potassium ferrocyanide) Underlying scientific foundation lies within chemistry and mineralogy/ crystallography • Not "quick and dirty" techniques
Which of the following methods is best for analyzing GSR
Scanning electron microscopy- energy dispersive spectroscopy
Backscatter electrons
Screenshot
Collection
Select the most direct and least intrusive technique(s) as possible. Common collection techniques include: Picking Lifting: Tapes and Rollers Scraping Vacuum sweeping Combing Clipping Washing
Flat Glass Breakage In Flexion
Sheet glass fracture Glass: -strong under compression -weak under tension
Non-wovens
Sheet, web, or batt of natural or man-made fibers or filaments, excluding paper that have NOT been converted into yarns, and are bonded to each other by any of several means" Examples: wipes, automotive carpets/ liners, among many others
ACE Comparison Iterative Process
Side-by-side comparison with appropriate area of known and questioned prints to determine if they are in agreement or disagreement • Based upon features, sequences, and spatial relationships within tolerances of clarity and distortion • All levels of details (starting with level 1) • In absence of indicators, all areas of available known impressions must be compared
Vegetable fibers
Sisal Coir Hemp Manila Flax Jute Cotton
Important factors for pattern formation
Size and placement of volar pad • Timing - Regression of volar pads vs ridge formation • Delta placement -Low pad: arch -high pad: whorl -intermediate: loop
SkinAnatomy
Skin - Epidermis - Outer protective layer Several layers of living cells (innermost) to dead cells (outermost) - - Dermis - - Inner layer of living cells Provides strength and flexibility
Soil Forming factors, Topography
Slope and aspect affect the moisture and temperature of soil.
Forensic Soils Analysis
Soil consists of many components; Rocks & minerals, Plant debris, Insects & insect contributions, Microorganisms. Chemical products of biological breakdown,Human additions (anthropogenic)unique particle principle
Method II
Solid reagent crystal is added to test solution. • Produces an excess of reagent at the beginning. • Good for double salt precipitates -creating concentration gradient producing ring of different concentrations -reagent is a sold then put reagent around it and see if crystals appear
Injection Molding (closed)
Soling material is injected into a tightly closed mold through a small port(s) - Soles may be molded individually and require attachment to upper at a later time - Soles may be molded directly around upper creating a complete shoe
Resolution
Specimen acts like a diffraction grating
Achromat
SphericalAberration: 1 color ChromaticAberration: 2 Colors
Fluorite
SphericalAberration: 2-3 color ChromaticAberration: 2-3 Colors
Apochromat
SphericalAberration: 3-4 color ChromaticAberration: 4-5 Colors
Forensic Hair Examination - Descriptive
Starting point is to attempt to eliminate the Q, to show that it is different, and not to start out looking for similarities1 Unaided eye Stereomicroscopy Light microscopy: Pattern Recognition Comparison Microscopy"There are no short cuts in hair examination... there is no substitute for a detailed and systematic examination."1"Side-by-side comparison of hairs is the only appropriate method to carry out the holistic pattern recognition process..." -Key points:Look for differences between K and Q (e.g., pigmentation is totally different)Use stereo light microscopy first, then brightfield microscopyif cannot exclude, then mount a representative number of hairs for comparison microscopyProceed systematically with comparison (it DOES take a long time to do side-by-side comparison ... e.g., headstamp of cartridge casings, impressions for toolmarks)
Ropes and Cordage -Terminology
Strand- several yarns twisted together Twine- strong thread consisting of two or more strands with diameter < 4 mm Rope-formed by twisting at least three strands together > 4 mm Core- fiber or group of fibers running lengthwise through center of a rope or twine May be parallel, twisted, cabled, or knitted but are not combined structurally with cordage Lay- Rope or twine direction of strands in a helix about rope or twine -Designated either S or Z (same as yarns) Length of lay - one complete turn of a strand which forms part of a rope or twine Angle of lay - angle formed between a strand and axis of a rope or twine
What is glass?
Substance used to manufacture windows, bottles, etc. -ASTM (American Society for Testing and Materials) -definition:Inorganic product of fusion which has cooled to a rigid condition without crystallizing.
In the evaluation stage of the ACE-V method, which of the following is a good description of an "exclusion?"
Sufficient features in disagreement to conclude two friction ridge impressions did not originate from the same source
In. evaluation stage of ACE-V method, which of the following is a good description of an "exclusion."
Sufficient features in disagreement to conclude two friction ridge impressions did not originate from the same source.
A scanning electron microscope with a energy dispersive spectrometer can provide which of the following types of information about a sample?
Surface features (topography) trace elemental composition
Polymers -Man-made Fibers: I
Synthetic polymers Condensation polymers Created when monomers bearing two reactive or functional groups from one or more compounds condense by normal chemical reaction to produce a linear polymer Addition polymers Created when monomers containing double bonds from one or more compounds add together at double bond to form a polymer confined to an aliphatic carbon chainPolyamides, aramids, polyesters, and polyurethanes Polyolefins and acrylics
Telogen
Telogen hairs are the easiest to identify.Microscopical features: club or spade-shaped root. -Q-tip
Soil forming factors, Climate:
Temperature and moisture amounts cause different patterns of weathering and leaching. Seasonal and daily changes in temperature affect moisture effectiveness, biological activity, rates of chemical reactions, and kinds of vegetation. -As it freezes it expands and tends to forms cracks in the rocks and can break the rocks down into smaller pieces and even soil
Flat Glass Usage
Tempered glass
Terminal Hair
Terminal: final stage of differentiation. What we typically think of in terms of human hair Two types: primary and secondary Primary (asexual): head, eyebrows, eye lashes, forearms, legs Secondary (sexual): pubic, axilla, beard Form in response of androgens -what we generally use for forensic examination -Key differentiation between primary and secondary: secondary is formed as result of hormones (arises from puberty.)
Diphenylamine
Test for nitrates and nitrites (and other oxidizing agents) - Reagent • 1 g DPA in 100 mL conc. H2SO4 - Test • Performed in porcelain spot plate • Reagent added to particles of suspected GSR • Production of blue color - Disadvantages • Reacts with numerous oxidizing agents! • Strongly corrosive! • Primarily of historical interest (dermal nitrate or paraffin test) -GSR
Uniaxial Crystals
Tetragonal and Hexagonal -We will treat natural and synthetic fibers as uniaxial crystals
Fiber Evidence Facts
Textile fibers and materials are mass produced When all variables (color, fiber type, etc.) are considered, there are an extremely large number of different fiber types in existence; thus, probability of finding any one particular type (unless very common) is low Some fiber types, colors, etc., are much more common than others Regional trends: Blue and White in State College Adherent fibers are most likely result of fairly recent associations Significance of fiber evidence can range from very low to very high but it is never zero (0) nor is it ever 100% conclusive
In the presentation to the characteristics of hair, we considered:
The hair follicle and the structures associated with itThe different structures from growth until it falls off the hair. -The different growth stages of hair -The microstructure of hair (esp. cortex) -The pigments and pigmentation -These are all very important characteristics to consider for what is considered EVIDENTIARY for forensic hair comparisonThe topics in this presentation are:Understanding the associative value of hair evidenceThe macroscopic features of hair (color, dye band, length, shaft characteristics)The microscopical observationsGrowth phaseMedulla patternsCortical featuresRacial ancestry (gross characteristics, weak individualizing at best)Somatic origin (which part of the body)Alterations to hair (incl. treatments and damage)Sample collection of hairTransferability and persistenceComparison of hair and interpretation
Cuticle Layers
The layers of a cuticle contain different structures, each to impart properties to protecting the hair AND to give it structure and shape. For example, a thicker cuticle will give a stiffer hair.
Melanocytes - pigment producing
The melanin are produced by melanocytes. These cells die off when the hair section they are in reaches maturity. -whats left behind are pigment bodies
Uniqueness of Ridge Configuration
The number of ridge units is random • Factors that affect ridge starts/ stops/ length are random. • Ridge unit location is random • Distribution of pores is random • Random growth factors
Fundamentals of the Uniaxial Optical Indicatrix (pgs80-81)
The optical indicatrix indicates how RI changes with vibration direction -Uniaxial: Prolateand oblate -All central sections are ellipses... expect 1 circular section -Normal to the circular section is the Optic Axis, also the c-axis for uniaxial crystals. -The O ray always vibrates perpendicular to the principal plane containing its path. -The E ray always vibrates within the principal plane containing its path -The O-wave normal direction and the O-ray path always coincide -The E-wave normal and the E-ray path generally do not coincide
Malleability:
The property of a material describing its ability to be shaped without fracturing
Hardness:
The property of a material describing its ability to resist being penetrated.
Distal End Characteristics
The proximal end of the hair is conventionally called the root of the hair. The other end of the hair is the distal end. The characteristics that you could find at the distal end include how the hair was cut, damage from the environment or treatments, etc.Left: cut end, flat, even ... could be from a pair of scissorsRight: sharp cuts, angled ... characteristic of a razor blade. Two angles of razor cuts are shown, wont be flat. -Can also round off
Resolution (Task #2)... Remember the 3 tasks?
The shortest distance between two points on a specimen that can still be distinguished by the detector as separate entities. -Don't want "empty magnification" -Consider the fine specimen detail to act as a diffraction grating -Unlike RI, the shorter the wavelength, the less diffraction
Crystal Growth
The three processes of crystal growth are divided into the following three stages1: 1. A driving force is applied, which causes the process to proceed by the formation of a supersaturated state. Too many ions in solution which must be removed= crystal formation 2. Particles smaller than some critical size are formed in the system. Some clusters grow larger than the critical size. This is called nucleation. 3. Once the critical size is exceeded, the crystals begin to grow from solution.
Light sources are very important in light microscopy. Tungsten-halogen light sources are black body radiators. Using the diagram provided, which of the following statements about black body radiators are true? NOTE: increasing the temp (K) is analogous to increasing the voltage through the tungsten lamp filament.)
The total radiant flux decreases as you increase the voltage to the tungsten filament. -The light emitted at 3300K has more visible light intensity than light emitted at 2500K
Transferability and Persistence
The y-axis is hair persistence on an article of clothing which we assume is a fabric. The x-axis is the length of time in hours for the wearing of the clothing by an individual. Q: Where have we seen this type of two-stage loss from a fabric before? ... yes, glass as forensic evidence
MicroscopicalObservations -Summation of Qualitative/ Descriptive Features
There are LOTS of microscopical observations that we can make about hair. When we look at the list of features, most of the notable ones are based on the morphology of hair which in turn is related to the growth of the hair from the follicles Q: Which microscopical observations would be better at individualizing a hair? Which ones for looking at environmental effects?--> Going to be difficult to individualize hair to an individual using microscopical methods Pigmentation-size, distribution, densityColor TreatmentsShaft CharacteristicsMedulla CuticleCortexRoot TypeDiameter (range)Proximal EndDistal EndAbnormalitiesArtifactsDamageAmong others...
Provide 4 ways (and locations) that ammunition can acquire toolmarks during the process of firing a gun
There are many different ways that ammunition can acquire toolmarks during the firing process. One way is a result from an extractor hook which is present under the rim of the head of the cartridge case. This is a hard metal tool that push or pulls the cartridge case out of the chamber. Since it is a hard metal it often scratches or impresses the area under the rim of a case during this firing process. Another way is due to the ejector. This push or kicks the cartridge case out of the opening in the slide or ejection port once it is extracted from the chamber. A firing pin may be used for the same purpose as the ejector which is a hard metal tool which is also known to impress the head of a case while firing a gun, leaving toolmarks. The chamber of a gun can also impress or scratch the surface of a cartridge case during firing. The chamber holds the cartridge in place during firing. Lastly, the lands cause the bullet to spin as it travels through and leaves the bore when the gun is fired. The land will leave marks on the ammunition and there will be no marks where the grooves are. Each section varies from every other section of the same land and groove, producing unique feature in the bore of the barrel.
Hair Curvature (Form)
There is a classification system for degree of "wavinesss" to hair. Type class 00 (straight) to 09 (very tight curls) NOTE: The more cylindrical the cross-section of a hair, the more likely it is to be straight. -Straight, curved, wavy, loose curl, and tight curl -Correlated with cross-sectional shape of hair shaft
Soil Mineral Material
Three main parts: Sand: 2,000-50 μm Silt: 50-2 μm Clay: < 2 μm Picture on how to classify soil based on size
Picking-Manual Isolation of Particles
Trace evidence may be separated from an item by using clean forceps, tungsten needle, magnet, or other micro-tools. -The collected samples should be immediately protected against loss or contamination. -Typically performed using stereomicroscopy (with boom stand) or surgical microscope -Isolate items placed in petri dishes, watch glasses, vials, or microscope slides -Strengths: Intimate knowledge of how evidence was on the item as well as where it came from (within the item)., ~Efficient: items are identified, recovered and isolated in a single step -Easy to focus on target evidence types (glass, blue fibers, propellant...) -Limitations: Time intensive = $$$, May cause unconscious bias
What are the qualities of hair that give them forensic evidentiary value?
Transfer - Can be transferred but most retained by the sourcePersistence - Retains its properties (that are useful for comparison and identification) AFTER the transferSecondary transfer - can work for or against hair as a useful source of forensic valueSize - small enough to be ignored, but large enough to be analyzed microscopicallyInter-sample variability - differs more between individuals (possibly) than within the same individual
A fiber with a positive (+) sign of elongation means that the slow ray vibrates parallel to the length of the fiber
True
Examples of man-made polymer synthesized by addition of monomers are polyolefins and acrylics
True
For light rays entering anisotropic materials, the slow ray vibrates perpendicular the the fast ray
True
Generally the medulla of animals is larger than humans, with some exceptions
True
In refraction of light rays, when we state "light bends as it enters the medium," we are really saying that light changes direction of travel
True
In the statement "isotropic materials have only one refractive index," we mean that isotropic materials have three refractive indices but all three have the same numerical value
True
Some class characteristics of footwear impressions include the shape, dimensions, and designs of the sole but does not include Schallamch patterns
True
T or F: Light Rays are a type of electromagnetic radiation. Electromagnetic waves have electric ad magnetic vectors that vibrate perpendicular to each
True
The major factors affecting glass particle transfer and persistence are garment type and position of the person relative to breaking window
True
To properly report a refractive index value, both the wavelength and temperature must be provided
True
When a crystal is viewed at 45 degrees off extinction between crossed polarizers, the transmission curve for the analyzer can be calculated using the following equation L=100sin^2(R/lambda)180 degrees
True
Cross-sectional shape can be a highly discriminatory variable for forensic fiber examinations.
True -non-cylindrical cross-sections can help determine whether the fiber is bicomponent, has internal structure, and can narrow down the source because some applications of fibers use different cross-sectional shapes.
When one reports a refractive index value for comparative analyses, they must provide both wavelength and temp
True, Refractive indices vary with wavelength of light and the temp at which its measured.
S twist
Twisted in a clockwise fashion when viewed along long axis of yarn An "S" can be superimposed on yarn and its center will align with direction of surface fibers
Z twist
Twisted in a counterclockwise fashion when viewed along long axis of yarn An "Z" can be superimposed on yarn and its center will align with direction of surface fibers
Igneous - Form from molten rock
Two Types Intrusive: granite, gabbro, .... Extrusive (from volcanos): rhyolite, basalt.... Igneous rock is created through volcanic formation. How new rock is generated through molten The slower the magma is cooled, the larger the crystal Through Lava flows or magma deposits -Formed by volcanic processes
UniaxialExtinction
Uniaxialminerals should appear dark when they are viewed along optic axis (axis is vertical or parallel to optic axis of microscope).
Cell Parameters
Unit cell edge lengths a,b,c -Angles (α,β,γ): -α= angle between b and c -β= angle between a and c -γ= angle between a and b
Wellman Machine
Uses a blade which travels around a template to cut soles from a sheet of soling material - Can only cut uncured, calendered rubber
Recovery of Fibers
Visual search with oblique lighting and removal of fibers with tweezers Ensure a clean working area that has a white or light-colored surface REMEMBER: photograph fiber(s) in situprior to removal or disturbance! Use of high-intensity, tunable wavelength light sources (e.g., ALS, CrimeScope, etc.) or UV light sources may prove valuable Tape lifts (or adhesive or gelatin lifters) NOTE: Preferred method after visual examination! Vacuuming Useful when a large area requires coverage Major drawback is material typically collected includes a large volume of old material ("historical")
Optic Sign: Which RI is the A.B.?
What did we learn? 1.The A.B. is α 2.βis closer to γ 3.γis the O.B.
Optic Sign: Which RI is the A.B.?
What did we learn? 1.The A.B. is γ 2.βis closer to α 3.αis the O.B.
Sedimentary
When igneous/ metamorphic rocks are exposed to: Weathering (every rock) Water Wind Hot/cold cycles Biological Botanical Microorganisms -Rocks keep getting broken apart and then are able to deposit into a sedimentary layer
Image Distortion
When magnification is not constant across the filed of view. -If magnification decreases with distance from the center: Barrel Distortion -If magnification increases with distance from the center: Pincushion Distortion.
Virtual Image:
When object distance is shorter than the focal length -Appears on same side as object -Upright -Cannot be projected onto a film/sensor plane -Examples include: Simple magnifying glass, jeweler's loupe, fingerprint examiner's loupe
Medulla - Black or White... It depends
Word of caution: The "color" of a medulla is not "black" ... it appears black because of the void space. -Maybe an air bubble
emitted when electron fills hole
X-rays
Melatope
a black or dark spot that marks in the field of view of the outcrop of light rays
Soil
a natural body consisting of layers or horizons of mineral and/or organic constituents of variable thicknesses, which differ from the parent material in their morphological, physical, chemical, and mineralogical properties and their biological characteristics. -Soils are named and classified on the basis of physical and chemical properties in their horizons (layers) -"Soil Taxonomy" uses color, texture, structure, and other properties of the surface two meters deep to key the soil into a classification system to help people use soil information. Can consist of different soil composition and does not have to be uniform throughout.
identify each of the following fingerprint characteristic as level 1, level 2, level 3 detail or none of them
a) general ridge pattern and configuration and ridge flow: level 1 b) path deviation and crease: level 3 c) ridge characteristics and spatial arrangement: level 2 d) ridge endings, bifurcation and enclosures: level 2 e) loop, whorl, arch: level 1
a good description of striation marks left by a tool is
an impression on a surface left by a tool as it slides across it.
The sources of natural fibers are paired with an example are paired. Select the correct pairings.
animal-angora vegetable- hemp vegetable- cotton mineral- asbestos
least common ridge pattern
arch
person linked to crime, another person, location or thing
associative
The triclinic crystallographic group is characterized by belonging to the biaxial crystal system and has three angles that are not 90 degrees and three refractive indices
biaxial not at 90 degrees three different
Isochromes
circles that connect points of identical interface colors -the interface figures for crystals of high birefringence possess more isochromes than do those for crystals of low birefringence
through which section of a biaxial indicatrix will you be viewing down one of the optic axes
circular section
In the image above of a fragment of glass, the types of fractures on the surface are:
concoidal fractures
To maximize the resolution in light microscopy, you should match the numerical aperture between the
condenser and the objective
controls resolution/ contrast
condensor aperture
most common seed fiber
cotton
The image above visually describes what type of distortion that occur in lens system
curvature of field
button rifling press
cutting groove -button rifling tool: little piece wider than hole in barrel (piece of titanium) pushed through barrel, forces rifling impression under high pressure
Burned hair
dark and blistered appearance (also, burnt hair smells awful!)
Trace evidence documentation include the following:
date and time of collection name of person(s) collecting the evidence unique identifier for each item collected descriptive listing of items
Organic GSR is derived from which of the following compounds
diphenylamine, Dibutyl phthalate, Nitrocellulose
does not follow snells law
e-ray
The pores are located on the ridge surfaces of the volar skin are
eccrine gland openings
For biaxial crystals, there are different refractive indicies. All crystal systems have at least one axis which is not 90 degrees from the others
false
rayon is a regenerated polyamide man -made fiber.
false
Color
for head hair, there is a general overall color, but even from your personal experience with your own hair or observing other people's hair, would you say that the color of a person's hair is uniform across the entire scalp? Is the hair uniform in color from root to tip?
Stamping
force to cut through metal, no heat -thinner sheets of metal cut into shape
these marks remained after the finishing process in the production of flathead screwdrivers. These lengthwise marks are consistent with which type of finishing process?
grinding
Limb hair: arm
has a natural taper towards the distal end, thinner diameter, exhibits similar pigmentation to other hair on the individual such as head hair (but not always true)The medulla can be present or absent, and when present, can exhibit an interrupted medulla
Human hair is primarily comprised of keratin. Keratin is:
has disulfide cross-linkages formed by cysteine side chains a polymer comprised of amino acids -generated in dermal papilla
Hammer forging
heat large pieces of metal and pound into shape with hammer -hammer may cause variations in the metal with each pound could be altered -not striated, just indentations and surface irregularities
Microcrystal tests:
inorganic and organic compounds (illicit drugs) - Produce precipitates that we can identify using microscopy: • crystal form/ habit, optical properties, subsequent tests -precipitates with crystal structure
SEM
instead os using light to make the image you're actually using electrons. Beam of electrons focused onto the sample Scanning electron beam over the sample. Different detectors (EDS) collect signals that are coming off that that point in the beam, generating a full image -Electron beam combines with sample to generate X-Rays: identifies what elements are present
Persistency
is required for forensic comparative science • This pertains to both repeatable (class) or unique (individualizing) features
Length of hair
it's common that most people have the same length for their head hair, but there can be considerable variation. Let's consider the cutting of hair
The above three images could be best described as (going from left to right):
knit, woven, nonwoven
Retardation
lag of slow ray relative to fast ray Derivation to Retardation: Δ = c(TN-Tn) Δ = cTN-cTn Velocities: CN= t/TNand Cn= t/Tn TN=t/CNand Tn= t/Cn Δ = ct/CN-ct/Cn Δ = t(c/cN-c/Cn) Recall: RI = cvac/cmedium Δ = t(N-n) Units are nanometers
Variation during mass production of shoe soles
large shoe companies may have more that one mold going at once -each machine may have subtle differences and imperfections creating sub class characteristics. -might also have subtle differences in textures in each mold and the molding method itself.
During the manufacture of plate glass, it is an annealed in a:
lehr
pore structure
level three detail
when collecting trace evidence, what is one advantage of lifting (tape/roller) over scraping methods?
lifting retains spatial orientation whereas scrapping does not
isochromes
lines that connect the points of identical interference colors in a conoscopic interference figure
enter on one side, recurve, and exit on the same side as entered
loop
When an object is places 48cm from the lens, it produces an image in sharp focus with a magnification of 0.5 What is the image distance? What is the focal length?
m=p/q 0.5=p/48 24cm=p=image distance 1/f=1/p+1/p ?
Crushed hair
mechanical crushing of the hair flattens out the hair and destroys useful information in that region of the hair (e.g., diameter, distribution of ovoid bodies, apparent pigmentation, etc.) Notice how easy it is to microscopically determine if a hair has been crushed if only part of the hair has been crushed.
polymer is molten, extruded, and solidifies by cooling
melt spun
Schists and gneisses are examples of what type of rocks
metamorphic
From a forensic science perspective, the evidentiary value of hair analysis (types of hair analysis) include
mitochondrial DNA analysis Determining country of origin nuclear DNA analysis on hair shafts differentiating animal hair from human hair
negative optic sign
n gamma - n beta < n beta - n alfa
positive optic sign
n gamma - n beta > n beta - n alfa
Dispersion n vs λ
n vs. λ -Refractive index is actually wavelength-dependent for any material. Different materials will produce a different "dispersion curve" (or Hartmann Plot) depending on the relationship between n and λ.
Snell's Law
n1sin(1) = n2sin(2) -Note that the angle -is measured relative to the normal (i.e. the surface perpendicular ). -When going from a high RI medium into a low RI medium, the ray is bent AWAY from the normal -When going from a low RI medium to a high RI medium, the ray is bent TOWARDS the normal -n refers to RI of whatever medium we are using -air (n1) to glass (n2) -theta would be angle of light as it travels -theta is always measured relative to the normal -High RI to low RI it always changes direction away from the normal and vice versa
Example Calculations snells
n1sin(1) = n2sin(2) 1.0*sin(40) = 3.912*sin(2) 0.642 = 3.912*sin(2)0.642/3.912 =sin(2) -Sin-1(0.1643) = 2 2= 9.457 Note frequency stays the same! Velocity and wavelength change*** (40 is incident angle)
The compounds found in unburnt, double base smokeless powders include
nitrocellulose nitroglycerine
Brewster's Angle
nr/ni=sinOi/sinOr When angle i is the complement of angle r or sin thetar= cos theatai get maximum polarization
first synthetic fiber made
nylon
Post mortem root banding (PMRB)
occurs after the death of the individual. This dark band appears near the root of the hair that is still attached to the follicle. This region is being investigated as to what is causing the dark structures to appear. It is speculated that microbial action in this nutrient rich area that protected by the follicle and the epidermis is degrading the proteins in the hair and creating gaseous micro-pockets of ammonia (gas - appears dark)
Extrusion
pasta maker
Magnetic and electric waves are always
perpendicular to each other
Using correct fingerprint analysis terminology, identify the following features of the ridge characteristics in the diagram above: points 1 and 4 are ending ridges
point 11 is a bifurcation point 3 is a dot point 7 is a short ridge
in general, most common synthetic textile fiber in 1995
polyester
In the images above, the left image is the interference figure of a uniaxial crystal under crossed polars. The right image is the same crystal under crossed polars. The right image is the same crystal under crossed polars with a full wave compensator (550 nm). The slow wave of the full wave compensators is vibrating in the SW-NE direction (w North towards the top of your screen). What is the optic sign of the crystal?
positive optic sign
The above image shows an opaque microscopic band near the root area of the hair from a decomposing body. What is that feature called?
post-mortem root banding
The above image is the distal end of human bread hair that has been recently cut. What type of cutting tool that was most likely used
razor blade
Fungal tunneling
recall that hair is mostly keratin and can serve as a source of food for microscopic organisms such as fungi. The fungi tunneling shown has dark lines perpendicular to the hair shaft and those are areas where the cuticle has been compromised by the fungi. The mycorrhiza are filamentous structures produced by the fungi to tunnel through the hair shaft
Hair dyeing
recall that there are dyes that can infiltrate the IMM such as Rhodamine 6G. Dyed hairs are easy to detect microscopically even when it appears to a "natural" color because of the evenness of the dye distribution in the shaft of the hair
limestone, sandstone, and conglomerate
sedimentary
The three primary categories of rocks are
sedimentary Igneeus metaporphic
Gang Broach
series of cutting edges that are forced through barrel. Each next broach is a little wider than the one before. rotating as it goes through -high probability that most barrels cut by the broach will be the same in each barrel cut. Sub class -grooves may or may not be individual -Land impressions are highly individual
Eyelash Hair
short length hair with a curved length (arc) and a natural distal end. Medulla can be variable.
natural leaf fiber
sisal
most common compositional type of glass
soda-lime-silicate glass
one of the sodium tests that results in a deep purple/pink in the presence of lead is:
sodium rhodizonate
Ksp,
solubility product constant at equilibrium -anything above ksp will result in precipitation - Solutions of reactants are mixed together to produce a precipitate. • The precipitate has a solubility of less than ~0.01 (1x10-2) moles per 1 liter of solvent (water). • AgCl Ksp = 1.8 x 10-10 @ 25°C • Ksp = [Ag+][Cl- ] = [1.34 x 10-5][1.34 x 10-5 • More general AxBy(s) ↔ xAy+(aq) + yBx- (aq) - Ksp = [Ay+]x[Bx- ]y
Dye band
some hair exhibits difference in color within the cortex because of the distribution of pigment granules (can vary based on the density of melanocytes at that time/stage of growth). this be related to nutrition/diet, Stress, Time of year (some have fewer melanocytes in summer)
The primary difference between a staple and a filament fiber is:
staples fibers are short length fibers, and filaments are long continuous fibers
According to the AFTE Theory of identification, the interpretation of individualization/ identification is
subjective in nature, founded on scientific principles and based on the examiner's training and experience.
retardation
t*(n2-n1)
The type of glass that breaks into relatively small, almost cube-like, pieces is called:
tempered glass
also known as safety glass
tempered glass
Eyebrow Hair
tends to be short (approx. 1cm -3 cm), exhibits a natural distal end (unless cut), can be treated, and macroscopically, tends to have an arc.
Beard hair
tends to have a thick medulla (but the MI is still about 0.33), but the cross-section tends to be triangular (gives a rougher texture). Also, given how beards are typically trimmed or shaven, the ends tend to exhibit razor cut edges
plane (or linearly) polarized light means
the direction of vibration of the light is in one direction and perpendicular to the direction of wave propagation
Shaft characteristics
the main one that we see macroscopically is the wave imparted on the hair which results from the hair growing out of the hair follicle with variation in the cross-sectional shape. Some people have straight hair, wavy, curly, tight curls, etc. Another macroscopic feature is the fineness or coarseness of the hair.
Describe the three optical indicatrices
the optical indicatriz is a representation of the direction and of the value of the refractive indicies in the crystal system. The length of the vecotr rdrawn from the center of the sphere (isotropic), ellipsoid (uniaxial) and the triuaxial ellipsiod (biaxial) represents the numerical value of the RI. The direction of the vector is the path that light ray takes as it tracels through the crystal.
Melanocytes are primarily responsible for
the pigmentation in the cortex of a human hair
Chest hair
there is a high degree of variability with chest hair from an individual. Different areas of the chest can have very different properties including degree of pigmentation, length of the chest hair, thickness (diameter), and medulla properties
Radial loops enter and exit on the _____ side of the hand while ulnar loops enter and exit on the ____ side of the hand
thumb little finger
For toolmark comparisons using the comparison microscope, it is important to adjust the illumination to be as similar as possible and to use the same magnification for both K and Q samples
true
The line perpendicular to the vibration direction of electromagnetic radiation is called the wave normal
true
Isogyre
two intersecting black bars that forms a cross
Why indicatrix is useful
useful conceptual tool to understand how the light ray interacts with the refractive indices within the crystal system. EX: in a uniaxial indicitrix, as the light interacts with the RIs epsiolom and w, the determination
not able to individualize footwear
wear pattern
Recent vs. recycled hair ...
what is recycled hair? This is hair that has been harvested from a donor and processed to make into products such as wigs or extensions. There can be chemical or mechanical treatments made to the hair to improve its desired properties and well as for preservation (e.g., straightening via chemical or heat treatment, dying to improve the color, etc.)
Growth Phases
~100,000 head hairs Not synchronized Shed ~100-150/ day
Types of Toolmarks Cutting:
• A combination of compression and sliding toolmarks. • Often have both excellent class characteristics and individual characteristics. Bolt Cutters Wire Cutters Shears/Snips
What is a Tool?
• An object that is harder than (and/or has a mechanical advantage over) another object • Example: Scratch a piece of plastic with a steel nail (tool). • Common tools in crime events include: screwdrivers, pry bars, chisels, wire cutters, saws, hammers, knives, guns, among many others. • Fingernail fragments treated as "toolmark" case • Always check for trace and biological evidence !
Surface Treatments and Textures to Mold Surfaces
• Applied for aesthetics and/ or functionality • Reproduced with each molded sole • Hand stippling - Molds are struck with a steel die by hand to produce stippled pattern in sole - Depths are irregular and deeper than acid etching - Positioning and features produce unique molds • Acid etching - Typically shallower than hand stippling with consistent depth - Produces random patterns • Sand blasting - Adds fine texture to sole - Commonly too fine to be observed in impression -very unique
Crystal Systems - Orthorhombic
• BiaxialAxes = 90o Refractive index directions parallel the crystallographic directions. -a does not equal b does not equal c -three different RI. One high one low one intermediate.
Variation created during Manufacturing
• Calendered (uncured) rubber processes - Shrinking, stretching, and distortion - Damage/marks created by handling before curing (vulcanization) - Incomplete pressing of design roller into rubber - Design roller damage which is transferred to rubber - If used, variations in die cutting or Wellman Machine cutting processes
Schallamach abrasion
• Caused by abrasion of the rubber • Lines of pattern form perpendicular to direction of abrasive force • These patterns are random and unique; thus, they can be used to individualize footwear • HOWEVER, they change rapidly with additional abrasion; therefore, caution must be used so that an exclusion is not made mistakenly
Individual Characteristics
• Damage - Cuts - Scratches - Tears/cracks - Holes - Portions of sole missing • Air bubbles (from molding process) • Additions to sole - Rocks - Gum - Tar - Sole patching material - Nails/tacks/staples, etc. - Vegetation
Electrical Discharge Machine
• Electrode plate is created in the shape/size of the sole design (created with CADCAM process) • Electrode is lowered onto metal mold blank and current passed through electrode causes erosion/burning of metal to form mold • Successive burning of molds cause continual loss of detail from the electrode -negative impression by burning mold into metal -electrode wears away over time, not exactly identical
Key Topics for the Analysis of Footwear Impression Evidence
• Enhancement • Manufacturing processes • Preparation of known impressions • Patterns of wear • Characteristics - Class - Individualizing • Comparison of impressions - Variation
Brief Introduction to the Manufacture of Tools
• Forming: - Forging, stamping • Cutting: - Shearing, Milling, Turning, Grinding, Filing, Broaching, Sawing, Drilling • Finishing: - Grinding and sandblasting
Methods for Manufacturing Molds
• Hand-milling or hand-engraving • CAD-CAM process • Casting • Electrical Discharge Machine (EDM)
Class Characteristics
• Includes the obvious: - Shape - Dimensions - Designs • Includes the not-so-obvious: - Repeated manufacturing characteristics - Example below: DIFFERENT class characteristics: tread width
Variation created during Manufacturing
• Manufacture of molds - Differences produced during handmilling/engraving - Differences produced by surface treatments • Hand stippling • Acid etching - Differences produced from casting methods
Casting
• Model of shoe made from metal, plastic, wood, or other material(s) and is made either by hand or CADCAM process • Model is then coated with a thin layer of metal (applied by spray) followed by covering with an epoxybased fill/aluminum resin • Model is removed after cast (mold) sets • Differences in models cause frequent differences in overall design characteristics-mold is negative impression. using negative (mold) to make a positive.
Variation created during Manufacturing
• Pre-molded soles - Different molds • Design • Texturing - Air bubbles - Problems during molding including contamination - Mold warping (due to stacking of soles) • COUNTLESS VARIATIONS POSSIBLE DUE TO THE WIDE RANGE OF DIFFERENT MANUFACTURING PROCESSES
Types of Toolmarks :Compression (aka Impression):
• Pressed straight into the substrate • Often have excellent class characteristics, but fewer individual characteristics. Hammers Pliers Punches/Chisels
Individual characteristics fingerprints
• Ridge characteristics and spatial arrangement • Ridge ending, bifurcation, dot, or combinations • AKA minutiae,Galton points, characteristic points, or points of identification Dimensional attributes of ridge,such as path deviation, width,shape, pores, edge contour, incipient ridges, breaks, creases,scars, and other permanent details
Types of Toolmarks: Sliding (aka Striated):
• Slides or scrapes across the surface, leaving a series of parallel scratches/striations • Often have minimal class characteristics but excellent individual characteristics. Pry Bars Screwdrivers Extrusion Dies
Tests for Lead (Pb)
• Sodium Rhodizonate • Bullet wipe/ impact • Yields deep purple/ pink for Pb, barium (Ba), and Antimony (Sb). • After the addition of hydrochloric acid (HCl), only Pb turns blue/purple. • Microgram sensitivity -pink and purple
Factors Affecting Tool Marks (impressions and striations)
• Tool Angle • Longitudinal Angle • Substrate Hardness • Pressure • Directionality • Path • Wear/ weathering • Alteration
Compression Molding (open)
• Two piece mold that may be hinged on one side; just like making waffles - Sole material placed into mold - Mold closed - Heat and pressure applied - Excess (flash) is trimmed - Example: Converse All-Stars
Crystal Systems - Monoclinic
•Biaxial •Monoclinic Bending one of the crystallographic axis so the angular relationship between a and c is not 90o -alpha and gamma is at 90, b is not -one angle is not 90o -a does not equal b does not qual c -Bending the crystallographic axis of "a" relative to "c" so the angular relationship between a and c is not 90o -The angular relationship between a and c is other than 90o. c-a does not equal 90o
Crystal Systems - Triclinic
•Biaxial •Triclinic •Triclinic crystals are complicated but that helps in identifying the material -provide info using optical microscopy - as light travels through it experiences different refractive indexes -No crystallographic axes are 90o -a does not equal b does not equal c •Example: Anorthite(Plagioclase) (CaAl2Si2O8)
Crystal Systems - Isometric
•Cubic a1 = a2= a3 Axes = 90o Corresponding negative direction of each axis -Growth dependent on: • concentration • access to face • other factors -Non-idealized crystal -grows along faces • Always sees same order of molecules • Collectively slows velocity of light • Light interacts with ions identically •Has one refractive index (actually 3 but all are same) -all angles are 90 degrees to each other -Ex: sodium chloride (cubic system) and HCl - due to this SYMMETRY, light will interact identically through the cubic crystal regardless of direction and orientation. Light will be slowed down the same amount through any direction
Upon discharge, firearms release various residues:
•Propellant (oGSR) •Primer (pGSR)
Cuticle
•Rectangular plates •Each plate is ~0.5 μm thick •Each plate is ~ 60 μm long •~3-6 plates thick -Outermost layer of the hair shaft The cuticle is a layer of flattened cells that form the outside of the hair sheath. The cuticle thickness differs from person to person. Key point:- When observing a hair with its length perpendicular to your view, the cuticle scales point away from the root of a hair.
Crystal Systems• triclinic
•This difference gives an extinction angle in a crystal, which can provide useful information for identifying the particle. -all three angles are not at 90 degrees -c-a does not equal 90o -a does not equal b does not equal c -NO axises are 90o •Examples: TATP, Baddeleyite(ZrO2)
Measuring RI in the Laboratory
•Use of the Becke line to determine the relativeRI between an object and the surrounding medium. •Halo effect around particle that moves into the medium of higher RI when focal distance* is increased. -When the focal distance is increased (i.e., the stage is lowered), the Beckeline moves toward the medium of higher RI. -if RI of glass is greater than RI of oil, it will act like a converging lens. If opposite then it will act as a diverging lens
Distortions caused by many factors including:
▪ Movements (slippage, twisting, pivoting, etc.) ▪ Double/multiple impressions ▪ Interference of other matter between footwear and target surface (e.g., vegetation, trash, pebbles, etc.) ▪ Target surfaces that are flexible or otherwise change when the impression is made (e.g., skin, fabric, etc.)
Variations
▪ No two impressions will ever be exactly the same in every detail! ▪ Caused by many factors including: ▪ Contact factors such as: ▪ Angle of footwear upon contact with target surface ▪ Point of initial contact with target surface ▪ Amount and distribution of weight ▪ Amount of residue, blood, ink, soil, etc. on footwear ▪ Condition of target surface
