CSI Final
Bullet wipe
- a dark ring around the perimeter of the entrance hole -dirt, lubricant, lead from projectile left behind on target as bullet passes through -NOT an indicator of distance
Shortwave UV
-180-254 nm -UV B/C -dangerous to skin and eyes -destroys DNA -good for viewing untreated latent prints (RUVIS system)
Longwave UV
-365-415 nm -UV A -good for both body fluids such as semen and saliva, which exhibit a green fluorescence -blood will appear black -no barrier filter is required for viewing but UV protective goggles should be worn to protect eyes
Dental stone casting techniques
-3D impression evidence such as tire and show marks in soil -sets harder and more forgiving of error during mixing and tends to recover more detail than the standard plaster -greater care is necessary when using plaster vs dental stone -impressions made in extremely loose soil, powders, or sand may benefit from treatment by a fixative -commercial fixatives: aerosaol shellac spray/ hairspray
Casting
-3D impressions have depth -typically cast using dental stone -made with gypsum, a while or yellowish mineral used in making plaster -never remove objects that are stuck in the impression -also snowstone -mixed with water and poured into impression and allowed to set -the reaction is exothermic and heat is released from the cast -thick layer of snow print wax is sprayed over the impression prior to casting
Violet/ blue light
-415-530 nm -bitemarks, bruises on skin ninhydrin (yellow filter) -fluorescein reactions with latent blood (yellow or orange filter) -urine, semen, saliva, many fibers, light colored hairs, fluorescent fingerprint powder (orange filter)
Orange/REad light
-570-700 nm -inks (red filter)
IR/heat/thermal
-700+ nm -questioned document exams -blood on dark substrates -help locate bodies, hot spots fire scenes -detect "fresh: latent prints
Bloodstain pattern
-A grouping or distribution of bloodstains that indicates through regular or repetitive form, order, or arrangement the manner in which the pattern was deposited. -the information gained from bloodstain patterns can be used for the reconstruction of incidents and the evaluation of the statements from witnesses and the crime participants
Standard methodology of fingerprint comparison
-ACE-V -analyze, compare, evaluate, verify
Dithiooxamide Test (DTO)
-DTO, ethanol and ammonium hydroxide -tests for copper (present in some bullets) -turns dark green where copper is present
Electrostatic dust lifting devices
-ESDL -various surfaces hold a positive charge, while the particles of the dust deposited are negatively charged. -mylar like film that is silver on one side -this greater charge in the film attracts the dust and dirt particles, transferring them from the weakly charged scene surface onto the lifting film -dust prints on floors, paper, carpets, and clothing
How ALS works
-LOOK AT DIAGRAM FROM BOOK -some energy from the ALS is reflected and some is absorbed -the absorbed light energy excites electrons in an object -as the electrons re-stabilize, they release energy as light at different (higher) wavelength than the original -using a barrier filter, the original wavelength is eliminated allowing only the converted wavelength to be viewed (fluorescence)
Blood enhancement of footwear imprints
-Luminol, Bluestar: fluoresces hemoglobin derivatives -leuco crystal violet (LCV), Diaminobenzidine (DAB): peroxidase activity of blood -Fuchsin Acid, amido black: protein content of blood: anything that is protein so have to be aware of false positives
RUVIS
-Reflected Ultraviolet Imaging System -allows the visualization of latent prints before dusting or development as well as visualization of other evidence such as latent footwear patterns -shortwave UV -nonporous surfaces: tile, metal, painted surfaces, plastic etc. -primary issue of success: adjusting the angle of incidence for the light source and ensuring a strong UV light source
Additional latent print development techniques
-Sudan black -crystal violet -MMD (multi-metal deposition) : uses colloidal gold and silver physical developer -silver nitrate solution -Acid Black1/Violet 17/ Yellow 7 -Vacuum metal deposition -5-MTN (methylthioninhydrin)
Important features of an ALS
-UV light can be damaging to DNA -PoliLight, Omnichrome, UltraLite, etc. work best for most body fluids at ~450nm, requires orange filter, not damaging to DNA -portability, size, weight, battery operated, light intensity, brightness, distance light will travel, spectra range, different evidence fluoresces at different wavelengths -cost: 40-20,000
Leucocrystal violet (LCV)
-a clear solution that turns a dark violet color where blood is present; the reduced form of crystal violet stain -for porous and non-porous surfaces -already contains fixative (pre-fixing still recommended for porous surfaces) -relatively safe chemical -reacts with heme; very sensitive -minimal background discoloration since solution is clear, however total background discoloration will slowly develop due to exposure to light and oxygen (natural oxidation) -if necessary, amido black can be used after LCV -enhance stains will fluoresce under various wavelengths
Gelatin Lift
-a low adhesive pad is smoothed over a 2D impression (fingerprints, footprints, dust marks and trace evidence) -a layer of gelatin in a pliable and flexible format is sandwiched between a rubber backing and a protective cover sheet -the thick gelatin layer is ideal for lifting evidence wile not sticking to the surrounding lift area -a clear acetate sheet is removed prior to lifting, and is replaced over the adhesive side in order to protect/preserve the impression once the lift is completed
Wetwop for adhesive tape
-a more recent development for dealing with adhesive tape is the Wetwop solution -the solution comes in both a dark and light color -the solution is brushed on the adhesive and left standing for approximately 15-30 sec -the tape is then washed in water to remove the excess Wetwop and then allowed to dry -the solution will react and adhere to any latent prints present, allowing them to be photographed
Constituents of a typical fingerprint
-a standard latent print left behind by an individual in the course of normal handling is made up of approximately 98% water -the remaining 2% is made up of oils, dirt, grease, and amino acids
Amido Black
-a water or methanol based protein stain that produces a dark blue-black color where blood is present -aqueous: best for non=porous surfaces, reacts with blood and certain proteins, but not a typical latent print; fixative can be added directly to reagent (not quite as effective); stained impression can be lifted with a fingerprint tape or gel lift -methanol based: both for porous and non porous surface, reacts with blood and certain other proteins, typically sharper results vs water, can damage or destroy certain substrates (paint/varnish), flammable/explosive/hazardous if inhaled
Adding machine paper technique for human skin
-adding-machine paper rolls, along with a variety of powders -the paper is quite porous and when in contact with the oils of a latent fingerprint, it readily absorbs them -advantage: will still work effectively when the body is slightly wet with condensation (morgue) -roll the paper with gentle pressure onto the area of the body -marks the tape identifying specific landmarks to ensure correct orientation
Friction ridge skin
-aids in grip and locomotion -palmar side of hand
Choosing the right powder
-always choose a powder that will provide maximum contrast between the fingerprint and the surface which it is deposited on -bichromatic powders will provide enough contrast on virtually any surface -examples of powders include black, white, fluorescent, and magnetic -green and red fluorescent powders (w/ALS) on a plastic container help to give contrast against the label and UPC symbol
Blood enhancement reagents
-amido black, LCV, DAB, fluorescein, luminol, crowle's double stain, coomassie brilliant blue, titanium oxide, hungarian red,
Angle of impact
-angle at which the blood drop strikes the surface of a target -a circular stain is created by blood striking surface at ~90 deg. -the pointed end of an elongated stain points to the direction of travel
Fingerprint classification
-application applied to fingerprint pattern interpretation, ridge counting, and ridge tracing
Lifting a print
-apply exposed edge to surface just beyond the print -roll a finger across the tape/lifter to cover the print in a smooth and steady motion -use additional pressure to eliminate air bubbles -remove adhesive in a smooth and steady motion (no hesitation or irregular movements)
Enhancing the bloodstain
-apply reagent in same fashion as fixative -rise when necessary: chemical and/or water rise -removes excess background staining, making impression clearer
Three basic fingerprint patterns
-arch, loop, and whorl
Satellite stains
-as blood strikes a surface, smaller droplets may break off and land near the parent stain
Photographing stains/impressions
-as is and after chemicals have been applied -scale should be in same plane as impression -indicate position/direction of impression in photograph -flash should be held at an angle to produce shadows/contrast -luminol photos may require up to a 5 min exposure time or 20sec to 1 min with a digital camera
Why is bloodstain pattern analysis useful?
-assist in determining manner of death -reconstruction of events -corroborate/disprove a story -may lead to discovery of additional evidence -determine which stains for DNA testing
Steps to bloodstain pattern analysis
-become familiar with scene -identify and categorize discrete patterns -evaluate directionality/motion -evaluate interrelationships between stains, evidence, etc. -if necessary. determine impact angle, point of convergence, area of origin -formulate theory to explain the above -documentation is essential -once the scene has been released, a complete and accurate bloodstain pattern analysis can be conducted but only if proper documentation has been completed
Applying fingerprint powder
-best to NOT dip brush directly into the powder jar -transfer a small amount of powder to a paper fold -with a powdered brush lightly stroke the desired area in a circular motion -excess powder should be removed -developed fingerprints may be enhanced using a fine bristle -over powdering and over brushing may destroy the fine detail
Cast-off stains
-blood flung or projected from an object in motion or suddenly stopped -linear or curvilinear -consistent parallel directional angles -consistent change in impact angle
Expirated blood
-blood forcefully expelled from the nose/mouth to clear airway; characterized by tiny, aerosolized stains
Arterial gushing and spurts
-blood under pressure from any breach in an artery -series of related spatter stains in a linear or curivilinear orientation -large volume evident -large elliptical stains
Skeletonized stain
-bloodstain that although disturbed, still reflects its original shape and size
IR filter/UV light for locating blood
-bloodstains may be difficult to see on dark or reddish substrates -blood absorbs all light, making it appear black -often the substrate will reflect some light back creating contrast
Contact shot
-bruising on skin in pattern of muzzle -star shaped/ stellate tear pattern around hole due to expansion of hot gases that enter the hole
Impression Evidence primary considerations
-can it be transported -does it need to be enhanced -what method/collect impression
Primary considerations when using chemical enhancement
-can the object containing the stain/impression be collected and transported to the lab intact -take photos first -usually best if feasible to transport whole item -what method will be used to enhance/collect/document the impression? -base on type and color of substrate, location, etc.
Labeling for fingerprint lifters
-case#, item description/#, date (time), person collecting, any processing technique utilized
Method for collect/document the impression
-casting, ESDL (electrostatic dist lifter), gel lift, photography first
2 inches or less
-charring/blackening -melting of synthetic fabrics -sooty deposits -skin tattooing
Before you leave a scene where footwear impression evidence was colelcted
-collect shoes from anyone who had access to the crime scene -victim, suspect, first responders, members of household, investigating officers, witnesses
Tool mark examination
-collect suspected tools if present -compared to test tool marks made at the lab from suspect -when collecting, be careful to examine for other evidence (paint, wood, trace)
NAS report
-committee was made up of forensic scientist, members of legal community, and scientists -findings: wide assortment of methods, practices, levels of training/education and available resources; forensic science research not well supported, lack of strong, unbiased federal leadership
Crime Scene Reports
-consolidates and summarizes relevant details that the crime scene technician thinks are important -not necessary or possible to include every single detail/action/observation from the scene -all details reported must be accurate -objectivity is critical -important features: accuracy, brevity, clarity -no typos, grammatical errors, run on sentences etc -must contain original signature or author and date/ e-sig -handwritten initials on every page -case number with all other case info -no brand names as generic terms, acronyms, slang etc. -relay info as facts and observations rather than opinions -avoid words like small/large -describe what you did or saw in the past tense; general descriptions may be in the present tense -don't include info not directly related to the crime scene or information learned at some other time
Magnetic powder
-contains coarse and fine iron grit, which collects at the end of the brush containing the magnet -the coarse iron grit forms the bristles and the fine particles develop latent prints -can only be used on non-ferrous items -typically used on fresh fingerprints
Difference between a broad band "blue light" and a standard ALS
-crime scene search (CSS) filter employ a broad pass band filter encompassing wavelengths between 390 and 520nm -with an orange barrier filter, will cause many biological fluids, hairs, and fibers to fluoresce -if engaging in a general fiber search. the technician should consider using a wide range of wavelengths, as no one wavelength affects every single dye encountered
Human Skin fingerprint collection
-dead on scene: adding machine paper technique, cyanoacrylate fuming, magnetic powder, iodine fuming -alive on scene: adding machine paper technique, smooth plate technique -wet surface: utilize the adding machine paper technique which is not negatively impacted by moisture
rubber casting compounds
-designed to capture microscopic details of tool mark impressions. -most effective when used on metals, wood, bone, or plastic. -Not effective for bite marks on human skin or for casting dirt impressions. -one base material and one curing compound
Fingerprints on Skin
-deteriorate rapidly on skin -it is best to fume the body within 24 hours of deposition of fingerprints -moving/placing body in body bag may damage prints
Small particle reagent
-developed to recover latent prints from wet surfaces -primarily molybdenum disulfide suspended in a water solution -the suspended particles react with and attach to the fats found in the latent print -SPR is sprayed over the surface a number of items, each time allowing the liquid to drain off -once the print begins to develop, the technician continues the spraying until sufficient contrast is achieved -the surface is then allowed to dry -effective on almost any nonporous surface -non-porous evidence found wet or immersed in a body of water is best processed at the scene; oxidation, rust, and a general breaking down of properties causes' quick and irreversible damage to evidence once it is removed from the water
DAB
-diaminobenzidine -produces a dark brown color where blood is present -hazardous (carcinogen) -very sensitive to heme -H2O2 required -works on porous and non-porous -will not transfer onto gel lift
Visual/ microscopic exam of gsr pattern
-distinct size, shape, appearance -black= unburned brown=burned/partially burned -handgun powder typically disc or flake
Primary types of evidence that respond to IR light
-documentation exam -bruises -IR reflective substrates can appear light so creates contrast
Hungarian Red
-dye that stains proteins in blood and other body fluids -best for non porous surfaces -has ability to fluoresce (green light with red filter) -stained impression can be lifted with a gel lift, but dye will diffuse over gel surface in time -relatively safe
Crystal Violet solution for adhesive tape
-easy to accomplish and produces outstanding results -create a stock solution by mixing approximately 1.5g of crystal violet powder in 100 ml of ethyl alcohol -adds 2ml per 100 ml of water to create a working solution -the tape is dipped or immersed in the working solution after which is is held under cold running tap water -crystal violet will react with any latent prints present, producing a blue or violet coloration that usually provides good contrast
Latent prints
-effectively invisible -occur as a result of oils and secretions from the friction ridge surfaces being deposited through contact -require development to visualize, but can occasionally be visualized with oblique lighting
Fluorescent powders
-enhance contrast -particularly useful on multicolored surfaces, where consistent contrast under normal lighting
Directionality determination
-entry or exit
Prior to blood enhancement
-examine stain with oblique white light, bright white light and ALS -photograph and measure -collect sample for serological/DNA testing (for trace evidence) -if stain is a pattern, choose an area that is smudged or unlikely to interfere with a pattern analysis -conduct a presumptive test for blood (one that reacts with heme, not protein) -test the enhancement reagent in an out of the way area -be sure the chemicals dont damage the surface or blend in with the color of the substrate -stains should be dry before applying any chemicals
Light
-exists as both a wave and a particle (photon) -visible light is the portion of the electromagnetic spectrum that we can visualize as colors -measure by the length of its wave in nm (distance from peak to peak) -nm= 1/10 to 9th -the lower the wavelength, the greater the energy -the greater the energy the greater the penetration -x-ray: penetrates living tissue and can cause cancer -mid range UV: from sunlight causes sunburn -white light and heat are not considered harmful
Choosing the right brush
-fiberglass brushes are typically used when searching for fingerprints -camel hair brushes are typically used in tight spaces and as a clean up brush - Marabou (stork) feather brushes are typically used when searching a large area for fingerprints and for fluorescent powders -magnetic wands are not actually brushes and must be used with magnetic powder
Types of fingerprint brushes
-fiberglass, camel/goat-hair brush, feather/maribou
Preparing for blood enhancement of a stain
-fixing the stain: DO FIRST -you will be applying a liquid to a blood stain and you want to make sure it isn't dissolved or washed away -use methanol or 5-sulphosalicyclic acid -use a pray bottle, wash bottle or total submersion -30 sec to 3 min, blood may turn brownish -allow excess fixative to drain off/dry before proceeding
Luminescence
-fluorescence: the wavelength of light is converted while exposed to an active energy source (ALS) -phosphorescence: the converted wavelength continues after removal of the energy source (glow in the dark stars)
Cyanoacrylate fuming (superglue fuming)
-fumes of the superglue react with the latent print, polymerization (plasticizing) and stabilizing the print -the fumed print can be dyed using rhodamine 6G, Androx, or basic yellow dyes which allow visualization and photography of significant detail in the minutiae -locks the latent prints to the surface of the evidence and preserves them until they can be further processed -DNA, drug identification, and fire arms are not hampered by cyanoacrylate fuming -trace evidence can be hampered -isolate item, superglue is placed within the isolation area, and the chemical reaction and fuming begins. Heat and humidity enhance and speed the fuming process, so a light or coffee-cup warmer are often employed as a heat source to speed the development
GSR testing
-gunshot residue refers to the residues discharged from the barrel of a gun when it is fired -unburned and partially burned particles of propellant -smoke -primer residues -particles of metal from projectile -powder may not be completely consumed during discharge and get embedded in clothing/tissue of victim
ALS can be used to locate different types of trace evidence:
-hairs -fibers -GSR -inks -drug residues -accelerants/explosives -body fluids
1 in to 18 in
-halo of smoke around hole (vaporous lead) -scatted unburned and partially burned gunpowder particles visually detectable
Contact to 1 inch
-heavy concentration of smoke around hole (vaporous lead) -scorch marks or melting of fabric -unburned and partially burned gunpowder particles in would track
Adhesive surfaces fingerprints
-if possible, submit to the crime lab -on scene: straighten the tape, if wadded consider freezing and/or solvents then straighten -then use: crystal violet, alcohol/water technique, sticky-side powders -match any treatment of the backing side of the tape (fabric, plastic/cellophane, paper) with the most appropriate process given its surface -wet surface: allow to dry and use any of the above
casting in snow
-if snow is wet/slushy, may need to add a thin layer of dry dental stone powder first -a light layer of dark spray paint can be applied to provide contrast for photos -snow may be used in place of some water to mix dental stone so that the temp of the mixture is closer to that of the impression
Distance determination
-if the results of such chemical testing are positive gsr on the evidence, comparison to test firings using the same firearm and similar ammunition can help to narrow the range of distance -nitrite patterns -measure diameter of the pattern on the evidence -conduct test firings at several known distances and compare -give result using a range usually ~1 ft
Crime Scene ethics
-illegal to alter a crime scene -anything removed from private property that is not covered by a properly executed search warrant is theft
NAS report reccomendations
-independent federal entity should be created and called national institute of forensic science; to establish standards and best practices, require mandatory accreditation and certification, promote peer-reviewed research, allocate funding etc. -establish standard terminology for reports and testimony: consistent with, match, similar, cannot be excluded etc. -fund peer-reviewed research in necessary areas -removal of all public forensic labs from control of law enforcement -research and develop SOPs to minimize bias and sources of human error -work with NIST and SWGs to improve reliability -mandate lab accreditation and certification of practitioners -QA/QC -national code of ethics -improve graduate education programs -improve medicolegal death investigation -nationwide fingerprint data interpretability
What are the two fundamental principles relating to friction ridge skin?
-individual and permanence -Individual: no two fingerprints have ever been found to be exactly the same; fingerprints are unique to the individual -Permanence: fingerprints develop about the third month of gestation and remain consistent throughout the life of an individual barring permanent damage to the papillary ridges or total decomposition
Sections of crime scene report
-introduction, characteristics, conditions, exits/entries, scene documentation, collection of evidence, evidence processing, results and conclusions
Tape Lift
-latent impression is first developed with fingerprint powder or other enhancement techniques -fingerprint lifting tape is smoothed over the impression -the tape with the impression is placed on a background that provides sufficient contrast
Ejected particles
-leave the gun at approximately the same velocity as the projectile but ate lightweight, have low mass and of poor ballistic shape
Stain shapes and approximate impact angles
-long elliptical stains: 10-30 deg -bear claw stains: 40-60 deg -circular: 70-90 deg.
Basic Bush and Powder
-mainstay method for recovering prints from large non-porous items (walls, furniture, floors) in the scene -not as simple as they look -loss of fingerprint evidence can be attributed to two issues related to brush-and-powder techniques -over powdering and too much pressure -works best on fresh fingerprints but also develop older prints -powder developed prints are always photographed in situ and collected with some form of lifting medium -careful to consider contamination: new brush, don't dip directly into jar -powder area until ridge detail becomes evident -contrast is a critical issue in selecting powder color
How do you become a bloodstain pattern expert?
-many 40 hour bloodstain pattern training courses available through govt, academic, and private agencies -basic and advanced courses -do not draw conclusions unless you have successfully completed adequate training and proficiency testing
track stance
-measurement of the distance between opposite side wheels -generally measured inside edge of the impression to outside edge of the opposite impression
Titanium dioxide
-methanol based solution that turns bloodstains white -best for non=porous surfaces -flammable/hazardous -stained impressions can be lifted with fingerprint tape or gel lift
Fingerprint identification
-method of analyzing, comparing, and evaluating a latent fingerprint to record or known fingerprints for the purpose of determining if there is a true match
Gelatin and other adhesive lifters
-most effective for two-d impression evidence -gelatin can be used on almost any surface -adhesive and rubber lifters are limited to recoveries from nonporous smooth surfaces like floors -gelatin lifters are more functional than their predecessors ; cost more and prone to damage in extreme temps
Specific issues related to tire mark impressions
-must capture not only the impression but whenever possible the associated data evident in the impressions -tire track stance, wheelbase, and turning radius
Range of fire determination
-muzzle to target distance -increase diameter = farther away
Fingerprints in fire scenes
-nearly every surface in a fire has been exposed to significant heat and soot -camphor technique: gentle flame, after which the soot was dusted off with a feather duster, thus exposing the print -long strand of masking tape that is rolled onto itself in a spiral and then burned -Thorton and Emmons developed a method: excess soot removed by gently washing it in tap water, the item is then re-examined, additional soot is removed with lifting tape (doesn't affect ridge detail because the print is heat fixed and stable)
Interpretation challenges with GSR
-nitrite compounds and lead from sources other than a firearm may be present and will test positive -a gun fired at close range may not leave any detectable residues on the target due to handling by emergency personnel, washed away by blood flow, wind/rain, intervening object, or specific gun/ammunition used
Chemicals used gsr pattern analysis
-nitrites: greiss test -copper: dithiooxamide test -lead: sodium rhodizonate test
The physically altered bloodstain principle
-once exposed, blood will react to environmental conditions (air flow, temp, humidity) in a predictable manner
Preservation of Fingerprints
-once the fingerprint has been identified, the fingerprint needs to be preserved (made permanent) -if the fingerprint is visible, comparison quality photographs should be taken before any processing is attempted -before a developed fingerprint is lifted, comparison quality photographs should be taken -camera must be on macro settings or close-ups will be blurry -choose appropriate color lifting tape and backing
OSAC
-organization of scientific area committees -collaborative effort with NIST and NIJ -purpose is to strengthen forensic science in the us through standards and guidelines -oversight by FSSB
Greiss test
-paper pre-treated with sulfanilic acid and 2-naphthylamine (alpha-naphthol) -garment placed face down on greiss paper -cheesecloth soaked in acetic acid placed on top of garment -hot iron applied for ~15-30 seconds -tests for nitrites (present in partially burned gunpowder) -test paper turns orange where nitrites are present
Porous surfaces and fingerprinting
-paper, cardboard, untreated wood -wrap it in paper, place it in an envelope or cardboard box and transport it to the crime laboratory where proper chemical treatments will produce the best results -field processing of this type of evidence usually results in damage and loss of evidence -iodine, ninhydrin, 1,8 diazfluoren (DFO) and physical developer can be used with porous surfaces
Drip patterns
-pattern caused when liquid blood drips into another liquid -consists of parent stain and round, raised satellite stains
Photographing using ALS
-photograph the item in white light first -if the stain is visible, examination quality photos should be taken -attach appropriate filter to camera lens and turn flash off -include same scale and identifier in before and after photos
Transfer method (bashinski)
-piece of dampened filter paper pressed on area containing hole -filter paper then chemically treated -good for dark or non porous items, or any item in which you do not want to apply the chemicals directly
What areas should be searched for fingerprints?
-points of entry/exit -areas where contact may have taken place
Factors to consider before processing for fingerprints
-points of entry/exit -areas where contact may have taken place -talk to initial officers -surface characteristics -constituents of the fingerprints -should the item be processed at the scene or collected and processed in the lab -packaging of item
Recovery of Fingerprints from Porous Items
-porous items include paper products and untreated woods -visual examination -Ninhydrin -Iodine fuming -DFO: 1,8-diazafluoren-9-one; reacts with amines; can be used prior to ninhydrin -physical developer
Basic types of surfaces encountered
-porous, nonporous smooth, nonporous rough, special conditions
Type of ammunition determination
-powder grain morphology -residue composition
Techniques a crime scene tech should be familiar with
-powdering -cyanoacrylate fuming (superglue fuming) -recovery of fingerprints on porous surfaces -recovery of fingerprints on human skin -small particle reagent (SPR) -various chemical enhancement techniques
When is chemical enhancement of blood necessary?
-primarily when impressions or patterns are present -to make faint or partial impressions more clear with greater detail -diluted blood (due to clean-up, blood separation, etc.) -to produce contrast when blood is on dark substrates or red substrates -to locate latent blood
Luminol: 3-aminophthalhydrazide
-produced light where blood is present -chemiluminescence: that can only be seen in total darkness -a molecule capable of fluorescing is excited, then releases energy in the form of light as it returns to its ground state -not permanent (1 to 2 min) -respraying the affected area is ok but luminescence will be dimmer -does not typically react with other body fluids, however false positives include metals, plant peroxidases and cleaners -works better on porous surfaces -sensitivity is 1:1000, 1:1million -works better on older, dried stains -does not interfere with dna testing
Coomassie Blue
-protein stain that dyes blood and other body fluids blue-violet -suitable for porous and non-porous surfaces -methanol base (can damage some surfaces) or methanol-water base -flammable/hazardous -stained impression can be lifted with a gel lift
Dye Stains
-provide additional contrast between the background/substrate surface and superglue fumed print -ideally the dye stain only reacts with the cyanoacrylate covered area -using various colored filters with an ALS set at different wavelengths, the dye stained print fluoresces
luminol
-reacts in the presence of heme by producing a chemiluminescence that has a blue green coloration -an oxidation reaction -false positives with metals, vegetable peroxidase and cleaning chemicals such as bleach -3-aminophthalhydrazide -immediate and intense reaction that dies out quickly: false positive -look for color, intensity, and duration
Fluorescein
-reacts with heme -must be viewed with ALS -fluoresces blue-green when viewed under 455-485nm using a yellow (or orange) filter -stains are sprayed with fluorescein followed by hydrogen peroxide: the finer the spray the better -a thickener can be added, making application to vertical surfaces less runny
Processing for fingerprints using Ninhydrin
-reacts with sweat, since it contains amino acids -fingerprints that react with ninhydrin form a colored product called Ruhemann's purple
Crowle's double stain
-red dye that stains proteins in blood and other body fluids -best for non=porous surfaces -has largely been replaced by hungarian red
Types of light
-reflected: white= all reflected -absorbed: black=all absorbed/none reflected -transmitted: light passes through when an item is transparent/translucent -converted: light can be converted from one wavelength to another , which is known as luminescence
How are results reported for gsr analysis
-residues were found which are consistent with: the passage of a bullet, the discharge of a firearm, a contact/close to contact shot
Methods for fingerprinting on human skin
-searching with an ALS -dusting with magnetic powders -cyanoacrylate fuming/dyestaining -iodine/silver plate method -iodine/silver plate method -ninhydrin -adding machine tape
Which body fluids will fluoresce?
-semen -saliva -urine -breast milk
turning radius
-smallest radius that a particular vehicle can turn in a circle
18 in to 36 in
-some scattered gunpowder particles
Wipe/altered stain
-stain created when an object moves through a preexisting bloodstain on another surface -i.e. paper towel wiping up stain
Pattern transfer
-stain created when wet bloody object comes in contact with another surface
Spatter
-surface tension must be overcome to produce spatter -force that pulls the molecules of a liquid toward its interior (decreases surface area, resists penetration) -blood spatter refers to random distribution of bloodstains that vary in size and may be produced by a variety of mechanisms -spatter doesn't include all bloodstains, so bloodstain pattern is preferred as a general term
Collection of tool marks
-take whole tool mark back to lab if possible -photograph (comparison quality if possible-multiple angles/ lighting conditions) -make a Mikrosil cast of the tool mark -mix casting material and hardener, use spatula to spread over tool mark, dries into a rubbery material after ~10 min -never attempt to place suspect tool into the unknown tool mark
To test first:
-target should be as close to evidentiary target as possible -tight weave/loose weave -similar garment can be purchased -cutting from actual item can be used
Three factors can have a negative impact on the recovery of fingerprints from skin
-temperature of the cadaver vs. temperature of the air -amount of hair on the suspected area -condensation of water on the body
Sodium Rhodizonate Test
-tests for lead -turns purple/violet -other metals may appear pink
Cyanoacrylate fuming
-the active ingredient in superglue is alkyl-2-cyanoacrylate ester -it is the cyanoacrylate ester fumes that will coat the item, making prints more visible and semipermanent -the prints may still be rubbed off if handled roughly -the items to be fumed are placed in the covered fuming tank, along with a dish containing a few drops of superglue -fuming time dependent on size of chamber and temperature and humidity -accelerated by heating the superglue and increasing the humidity in the tank -prints can be further enhanced by dye staining or powdering
casting in soil
-the cast should not be cleaned at the scene: dirt from the cast should be retained at the lab in order to compare it to any debris recovered from suspect's/victim's shoes
3 underlying principles that guide the behavior of the bloodstain pattern analyst
-the pattern diversity principle -the principle of stain shape and vector correlation -the physically altered bloodstain principle (PAB)
In order to achieve the best results using powdering techniques
-the right brush must be chosen -use the appropriate amount of pressure when dusting -choosing the appropriate powder -being careful not to over powder -being careful not to over brush
The principle of stain shape and vector correlation
-the shape of certain bloodstains provides indicators as to the direction of deposition as well as to the spatial origin of the blood -circular vs elliptical -spatter -the ratio between the length of the long and short axes of the resulting stain has an empirical relationship to the angle at which the droplet struck the target
What is friction ridge skin and where is it located?
-the skin that covers the underside of the fingers, hands, toes and soles of the feet -it consists of raised areas called ridges and the recesses between called furrows
The pattern diversity principle
-the variations in combinations of blood volumes and forces acting on those volumes lead to recognizable classes of patterns -when a blood mass comes under external force, the fluid's behavior under this force leads to the creation of recurring patterns
Purpose of ALS/chemical enhancement
-to locate stains/impressions -to make stains/impressions more visible in photographs -to enrich the details of a stain/impression that may require a comparison
Swipe/altered stain
-transfer of blood onto a target by a moving object that is bloodstained -i.e. bloody hand swiped across wall
What are the steps used to photograph an impression prior to casting it?
-tripod -camera squared to impression -scale of reference -proper framing -fill flash oblique lighting
Plastic prints
-true dimensional impressions -result from when friction ridge surface is impressed into a pliable material such as window putty
Dye stains and cyanoacrylate stabilized prints
-two dyes most often used: basic yellow 40 or rhodamine 6G, Ardox and P-Methoxybenzlamino-4Notrobenz-2-Oxa-1,3 Diazile (RAM) -Basic Yellow 40: submersion solution -RAM: best purchased premixed
gunshot residues on a target can provide clues as to
-type of ammunition, range of fire, directionality
Small Particle Reagent (SPR)
-used on wet items that cannot be allowed to air dry -consists of molybdenum disulfide (MoS2) suspended in a water and PhotoFlo solution -small black particles adhere to the sebaceous (fatty) constituents of fingerprints -prints appear gray/black on light colored surfaces and light gray on dark colored surfaces -recovered prints should be photographed before any attempts to lift
ESDL
-used to lift dust 2D impressions from dry non metallic surfaces such as floors, walls, carpets, doors, counter tops, etc. -a sheet of mylar film is placed over dust impression, black side down -a roller is used to press film firmly against impression -electrostatic charge is applied to the film using a high-voltage electrode -a charge difference between the dust and mylar sheet causes the dust to adhere to the film -the lifted impression is carefully rolled up and transported back to the lab for photography -the impression is photographed using oblique lighting techniques
Nonporous smooth surfaces
-varnished and painted surfaces, plastic surfaces, glass, metals, ceramics, guns, knives, bottles, finished wood -stabilization of latent prints and transport to the lab is the best approach for collection of this type of evidence -cyanoacrylate fuming (superglue fuming) -standard brush and powder techniques are effective and dye stains: Rhodamine 6G, Ardox and 7-(p-Methoxybenzlamino)-4-notrobenz-2-oxa-1,3-diazile (RAM) -fluorescent powders with ALs can also be used -SPR can be used on wet surfaces
Nonporous rough surfaces
-vinyl, leather, textured countertops, and other textured surfaces -cyanoacrylate fuming followed by dye staining -standard lifters do not work very well (tape and hinge lifters) -silicone and rough surface lifters should be used -gel lifters
Patent prints
-visible prints -result from friction ride surfaces that are contaminated in some fashion (blood, paint) coming into contact with another surface
stippling or tattooing
-when a firearm is discharged at close range -gunpowder particles become embedded in the skin, causing burns and abrasions
AFIS
Automated Fingerprint Identification System -computer driven fingerprint storage , search and retrieval system capable of data basing hundreds of millions of record fingerprint cards nationwide
SWGFAST
Scientific Working Group on Friction Ridge Analysis, Study, and Technology
What are fingerprints?
an imprint/impressions of the friction ridge skin of all or any part of the finger
wheelbase
measurement from the center of a front wheel to the center of the same side rear wheel
What shape does blood take when falling?
sphere
