Intro to Forensics Final

the analysis:

1)carefully planned experiments 2)use surface material comparable to the scene 3)trace direction, dropping distance, and angles 4)shapes of blood spatter is either round, or ellipse to oval shape

collecting dried blood samples

1)cutting-cut out a portion of the item with bloodstain; cut out control area 2)tape lifting-just like fingerprint lifting; lift a control area 3)scraping-placed into a paper packet; removed with sharp sterile razor 4)absorbing#1-moistened .5''threads; distilled/deionized water; packed in paper envelope 5)absorbing#2-moistened .5'' by .5'' square; place in envelope

scientific method

1)describe the problem(observations, research) 2)create a hypothesis 3)design experiments(want to make hypothesis fail) 4)collect experimental data 5)draw conclusions 6)test again if necessary

main goal of hair evidence

1)determine origin; 2)who the hair came from ; using a comparison microscope the origin and from whom can be determined

order of trying to develop prints

1)fume with iodine; 2)ninhydrin; 3)physical developer; 4) super-glue

drop size and velocity

1)greater than 6mm=large drop:gravity 2)2-6mm=medium:splashing of blood near the victim 3).1-2mm=fine drop:high velocity, coughed up by victim 4)less than .1=mist:high powered rifle

why is hair an excellent piece of forensic evidence?

1)high resistance to chemical decomposition; 2) retains structural characteristics over long period of time

spatter analysis: in order to reconstruct the crime scene, the csi must record:

1)location of blood, 2) distribution of blood, 3)appearance of blood

analysis starts with:

1)position with respect to other objects 2)shape of the blood spatter 3) pattern

identify hair pattern using:

1)scanning electron microscope(SEM); 2)compound microscope:make a cast in a soft medium

types of bullets

1)wad cutter-jacketed and plain lead; 2)hoxie(ball and end); 3)jacketed flat-nose; 4)round nose; 5)hollow tips; 6)talons:spread like the talons of an eagle(cop killers); 7)armor piercing - teflon jacket, tungsten tip(harder than steel), 45 caliber

types of impressions(tool marks)

2d, 3d and striation marks

Loops

5 key parts to look for: ridge ending, bifurcation, enclosures, short ridge(island), dot; Radial Loop: towards the thumb; Ulnar Loop: away from the thumb

Atomic Absorption

AAS: atomic absorption spectroscopy; used to measure a large variety of materials-metals, pottery, glass; destroys the sample; need 10mg to run a test; the sample MUST be accurately weighed; dissolved in a strong acid; resulting solution is sprayed into a flame of the instrument and atomized; light of a suitable wavelength for a particular element is shone through the flame; the amount of light absorbed is proportional to to the concentration of the element; measurements are made separately for each element of interest; very sensitive and can measure trace elements down to the part er million level; can measure elements present in minor and major amounts

PCR technique for a number of clinical and forensic applications

The product rule: using probability and eye witness - hair color, height, race, eye color, gender, etc...

transmission

a direct measurement of light (through the sample)

short wavelengths have

a greater number of cycles, hence have a higher frequency

chain of custody or possession

a list of all the persons that come in contact with the evidence; must be maintained where ever evidence is presented in court as an exhibit; a break in the chain of custody could result in the data being ruled inadmissible in court

medullary index

a ratio of the medulla diameter with respect to the diameter of the hair

scattering

a separation of light

spectroscopy

absorption spectroscopy is base on the fact that molecules absorb light; the wavelengths are absorbed and the efficiency of absorption depends on both the structure and the environment of the molecule; light= non-homogenous mixture of colors that can be viewed when shined through a prism which extends from red to violet;

can racial origin be determined?

african american-usually kinky, with dense unevenly distributed pigment; cross section = flat to oval; caucasion-straight to wavy with fine/coarse pigments more evenly distributed; cross section=oval/round

can age and sex be determined?

age cannot be determined(only infant); hair dyes, styles and length may suggest sex but these are class characteristics; from DNA from the root or tissues attached can sex be determined.

stereo microscope

aka dissecting microscope; camera adapted, ocular lens(10x),"objective lens(1-4x)

silver powder

aluminum; dark colored surfaces, mirrored surfaces, polished surfaces; these surfaces photograph black

bloody prints

amino black; hungarian red; patent blue; leuccocrystal violet; fuschin acid dye; dont interfere with DNA analysis;

spectroscopic methods

analytical techniques;interaction of radiation and matter; use light(radiant heat)

detection of prints with powders

applied with camel hair or fiberglass brush; different powders for different surfaces; select powder based on contrasting surface

physical science unit

applies chemistry, physics and geology to identify and compare evidence

individual characteristics

associated with a single source - tire marks, footwear impressions, tool marks(hard object in contact with a soft object), broken objects fit, fingerprint

AA

atomic absorption

distance determination

based on powder distribution, spread of powder, spread of shot, and burn intensity of the skin

bite marks

bites into a soft object are like a fingerprint(skin is the exception); skin bites lack finite details but may reveal dna(saliva)

cast off

blood that travels from a weapon to a surface(weapons=fist, knife, bat, hammer etc)

physical evidence includes

blood, semen, saliva, documents, drugs, explosives, fingerprints, fibers, firearms and ammunition, glass, hair, impressions, organs, paint, serial numbers, soil, tool marks, etc...

scanning electron microscope(SEM)

bombards sample with electrons; samples are prepared in a vacuum; reflects an image

packing should avoid

breakage, spoilage, contamination

firearm identification includes:

bullet comparisons, knowledge of weapons, restoration of removed serial numbers, GSR characterization(garments and skin), muzzle to target estimations

direction

can be determined by shape; pointed end always faces the direction of travel

class characteristics

can only be associated with a group; cannot by associated with a single source; example: paint: analysis of a single layer or blood: origin, type etc...

what to include in sketches

case #, name of suspect, name of victim, investigators, person drawing, date, approximate time, SCALE, distance between items, locations noted, reference points, LEGEND(key), compass

black powder

charcoal, graphite, zinc; light colored surfaces

sketches

clarify crime scene; not architectural; illustrative diagram; two people per sketch;one draws, one measures; back up photographs with respect to evidence, location and relation; demonstrate an overall layout of the scene; may focus on important details; topography may be illustrated; record of conditions

obtaining trace evidence

collect clothing as soon as possible-suspects and victims; when they undress, stand on clean white paper-reflects all light and makes trace evidence visible

evidence collection unit

collecting and preserving evidence and documenting crime scene

medulla

collection of cells; runs through the center of the hair; occupies 1/3 or more of the hairs diameter; not all hairs have a medulla; humans either have fragmented pr absent medulla; rarely do humans have continuous medulla

trace evidence goals

collection, preservation, identification, and use of material

microscopes

compound, stereomicroscope, comparison, polarizing, scanning electron microscope(SEM)

3D

compression marks; indentations caused when a hard object comes in contact with a soft

Whorls

consists of a minimum of two deltas; Plain whorl:symmetrical deltas-circular pattern; Central pocket whorl: asymmetric deltas; Double loop whorl: s-shaped-least common, 2 loops, 2 deltas;

transfer blood stains

contact bleeding, swipe(fall), smear(struggle) and wipe(cleaning)

cortex

contained within the cuticle; made up of spindle-like cells; aligned in a regular array (parallel to the length of the hair); the most important(forensically); embedded with pigment granules that impart hair with color; the color, shape and distribution of the granules are of great interest; examined microscopically; light reflected off the surface is minimized; light passing through the hair is optimized

root

contains tools for hair growth; grows in three phases; 1)anagen; 2) catagen; 3) telogen

three parts of hair

cuticle, cortex and medulla - are of greatest forensic interest

human medulla

cylindrical

cartridge bottoms

date, brand, caliber(arsenal), primer

priority of data collection

delicate items first-fingerprints, dust prints, blood, trace, larger items;

determining point of origin

determine angles of blood; determine the intersection of angles; point where angles intersect, show point of origin

goal in fiber analysis

determine the origin and number of sources from which the fiber comes from

identification of physical properties

determine the physical and chemical identities - test the known standards

determine paper chromatography values

determine the ratio of the front value(Rf)

refractive index

determined by the ratio of light in a vacuum to that of the light in the medium (velocity of light in vacuum/velocity of light in medium) water=1.3333- light travels 1.3333 times faster in the vacuum than in the water medium

angle

determined using trig; distance=not important; measure width and length and divide and express as a sine function(w/h=sin(theta))

ninhydrin

develop porous surfaces; reacts with amino acids; purple/blue color; 3hr for most prints to appear; speed up with heat; good for detecting old prints; most popular

francis galton

developed and classified fingerprints; rules of classification are still used today

chromatography

developed by russian botanist; used for separating plant pigments; process of separating chemicals by molecular mass, charge or solubility

Sir Edward Richard Henry

developed classification used in the US today

refraction

direction change of light (angular)

rifling-caliber

distance between two lands; recorded in the hundredths of an inch, or in millimeters .38 or 9mil; measurements are not of an exact number

Rf=

distance solute moves/distance solvent moves (always measure from the center of the circle/oval)

biology unit

dna profiling, blood stains, material identification, hairs and fibers

observe(take notes on):

doors(open, closed, locked, keys in etc); windows, lights, shades/blinds, odors, signs of activity, date and time indicators

collecting blood samples

dress appropriately-gloves, mask, body suit, goggles

passive blood stains

drops, drip patterns, pools

the crime scene

dynamic; first officer must pay attention to countless details; potential to disrupt the scene; success may be based on the steps and actions taken by the first officer; majority of evidence is obtained; provides investigators with a starting point; must prevent alteration or destruction of evidence; always assume that the criminals have left evidence behind; don't approach the scene with haste, be calm and deliberate; expect the worst, use caution; approaching with open mind can prevent carelessness

bullet comparisons

each gun has its own inner surface markings; the inner surface markings score the bullet as it leaves the barrel; test fire a bullet and compare the markings; if there is a match, you have the gun/suspect; individual characteristic(striations and markings)

Arches

enter on one side of the finger, travel upward in the middle and back down the other; Plain arch: most common, simplest, mild bulge; tented arch: acts like a pole in the middle, least common

how to properly enter the scene

estimate what has happened; avoid touching anything-doors, handles, light switches etc

collecting and packing evidence

evidence to be preserved so that it arrives at the lab in the same manner in which it was found; avoid-contaminating, breakage, evaporation, scratching and bending; each piece of evidence gets packaged separately and in different packaging

firearms unit

examines firearms, bullets, shells etc

iodine fuming

expose latent prints to iodine vapors(yellow-orange in color); sublimation:solid to gas; not permanent; photograph quickly; enhance or fix with starch(blue/black in color)

long wavelengths have

fewer cycles, hence are considered low frequency

vacuum sweeping

filter attachment, metal screen with filter paper, attached to regular vacuum, filter paper/screen=bagged and tagged

foreign matter prints

finger contacts dust and is transferred to a clean object, blood, dye, wet paint etc

the specifics of packing

fingerprints should not contact anything(package slides); tool marks(oil from rust if no trace, prevent moisture); clothing with biological evidence(protected from rubbing or being broken) victim clothing is packaged separate from suspect clothing; garments with fibers/hairs should be packaged separate from each other; firearms should be rigidly fixed; cartridge casing and bullets packaged; stomach and organs packaged in glass containers in a preservative; controlled substances packaged in vials, cushioned and topped with cotton; charred documents individually packaged, cushioned with cotton; CANNOT OVER PACKAGE EVIDENCE

pull the trigger of a gun and:

firing pin strikes the primer, ignites the powder, gas expansion, propels the bullet forward-as the bullet moves forward the casing moves backward with an equal force; strikes the breech block marking the casing; the shell gets marked by the metal surfaces of the firing and loading mechanisms, the firing pin will mark the primer uniquely, the firing pin is still a class characteristic, the breechblock markings are individual characteristics

emission

florescent spectroscopy

florescent powders

florescent under UV light(emit light when exposed); photograph and the background does not alter the clarity

gun shot residue(GSR)

found on the shooter, primer identification, most primers are lead, barium, and antimony based(except .22); found on the thumb web and back of the hand, palms, back of gun; swab the hand with 5% nitric acid; use atomic absorption spectroscopy to determine presence and concentration; SEM coupled with an xray

plastic fingerprints

fresh paint, mud, blood, candle wax, soap, adhesive tape(most common), tar

natural fibers

from plant/animal sources; animal based is the most common-sheep, goats, camels, alpaca, llamas, mink, beaver, rabbit

GC-MS

gas chromatography-mass spectroscopy

cuticle

gives hair longevity; outer most protective layer; overlapping scales; scales point toward tip; overlapping cells that have keratin; animal hair looks like shingles on a roof; scale pattern varies from animal to animal; used to identify as human only;

catagen

grows at decreasing rate; 2-3 week process; these roots have an elongated appearance

most common types of trace evidence

hair, fiber, paint, gsr(gun shot residue), soil, glass

handwriting

hand, electronic or typewriter(individualized); handwriting=personalized to the writer; typewriters and printers imprint the paper in different ways

documentation examination

handwriting, typewriting, printer analysis; authenticity; tests paper, ink and indented writing patterns; erased or charred documents

cartridge casings-revolver

has a lip at the base of the cartridge

searching the scene

have appropriate equipment; two csi should search(safety and get more evidence); csi should be used to working together; avoid night searches; use a systematic means of searching

latent fingerprints

hidden, unseen or concealed; must be enhanced/developed; composed of perspiration: 99% water, body oils amino acids, etc

HPLC

high performance liquid chromatography

what to consider in a search

how to conduct search; what needs to be photographed; where are possible sources of physical evidence are

comparing fibers

if original source exists, torn edges can be lined up under a microscope - colors/dyes, striations, chemical composition, refractive index of the fiber, spectroscopy

IR

infrared spectroscopy

gas chromatography(GC)

inject sample; moves through heated column; moves with assistance of a carrier gas(He); sample is vaporized; detector; computer

automated firearm search systems

integrated ballistic identification system(IBIS) - contains more than 800,000 images of spent cartridges and fired bullets

edmond locard

integrated scientific techniques into the crime lab; locards exchange principle

magnetic powder

iron; silver-black, bristle free brush-magna brush; leather/rough plastics;

before the impression is made...

it is photographed; side lighting aids in enhancing image; florescent image powders and light enhance impressions

determining the number of lands and grooves from a bullet

know the caliber, measure groove impression, measure land impression; caliber/groove impression+diameter)x3.14; 6 lands and 6 grooves in the barrel of the gun

contact area

large stain on a surface; caused by body contact

anagen

lasts up to 6 years; the root is attached to follicle for continued growth; gives the root bulb a flamed look

equipment for sketching

lead pencil is ideal, colored pencils, graph paper is ideal, clipboard, rulers, tape measures(50-100ft), compass

firearms and ammunition at the scene

leave it alone, allow the investigation team to handle it, never pick up a pistol by inserting a stick into the barrel(evidence in the barrel may become dislodged) pick it up by checkered part of the grip with 2 fingers, do NOT pull back the slide or touch the trigger(unless hot scene...unload to protect)

dust impressions

lift using electrostatic lifting device; mylan film; rolled with a roller; charged; enhanced with a developer; photograph

polarizing

light of a single plane; vibrates by: transmission, refraction, reflection and scattering; geological samples; used for analyzing stress levels in glass

the barrel of the gun

made of a single bar of steel, drilled out; after drilling, there are irregular random striations(no two barrels are the same); the inner surface is impressed with spiral grooves known as rifling; there are several techniques for rifling(button, mandrel etc)

fibers

man made fibers can be found in clothing, carpeting, drapes, wigs, football turf, etc

trace evidence on clothing

microscopic/macroscopic evidence; material clings via static electricity; caught in the fabric(washing embeds it even more)

identification of fibers is based on

morphological information and color using microscopes to compare standards

plant fibers

most common=cotton; undyed, white cotton fibers=super common they are almost meaningless; only rare dyes are of forensic interest

packing

multiple objects should be packaged individually; clearly mark contents; cushion objects; marked with recovering officer's initials and date collected; objects are tagged;

csi characteristics

must be detailed oriented, thorough; minimize mistakes; have good intuition

a good csi

must not allow influence from superior officers alter their search; must maintain knowledge on methods of locating and preserving physical evidence; when beginning a search, stand back at an appropriate vantage pint on the periphery of the scene and formulate a plan

types of fibers

natural and man made

tool marks are individualized by

nicks, breaks or wear patterns of a particular tool; and by microscopic irregularities(barrel of a gun)

cartridge casings-semiautomatic

no lip at the base of the cartridge

super-glue fuming

non-porous surfaces; metals, tape, plastic bags etc; cyanoacrylate vapors form when heated or reacted with a base; a white appearing print; enhanced with rhodamine 6G and UV light;

forensic nurses

nursing background, criminal justice, evidence collection, sexual assault

compound microscope

ocular lens, objective lens, stage, diaphragm, base, arm, course and fine adjustment; used for basic analyses

specialized personnel includes:

officers and detectives, csi, fbi, atf,dea,identification officers:photography and fingerprint collection, forensic surveyors:detailed sketches, photographers:ground, aerial etc,

forensic evidence

officially approved information; the information of fact, typically a jury considers when defending innocence or guilt; keeps the information away from the fact that due to some legally perceived flaw in the information; title used to distinguish from non-scientific information; scientific-dna, footprint, impressions, hairs, fingerprints

quantized energy

only a small amount of energy can be absorbed or emitted by atoms; (quantum=fixed amount)

types of sketches

overview of floor plan sketch-easiest, everything is on the same plane, final drawing; elevation sketch-when vertical plane is of interest, blood stains on wall; cross projection or exploded-similar to floor plan, walls are folded down onto same plane; perspective drawing-3D, must have artistic skills;

techniques for chromatography

paper, thin layer(TLC), column, gas, liquid(HPLC)

types of chromatography

partition, absorption, ion exchange, molecular sieve(gel), affinity

medical examiner(coroner)

pathologist, autopsies, time of death

light as a wavelength consists of

perpendicular electric and magnetic fields which oscillate sinusoidally as they are propagated through space

locard's exchange principle

perpetrators of a crime will bring something to the crime scene and leave something from it

preservation of developed prints

photograph; camera must have a close up lens; ideal camera has a fixed scale; cover with cellophane; attached to a colored cardboard backer

hair

physical evidence; not morphologically possible to individualize; chemical properties(color) and structure are the forensic features; can place an individual at the scene; must have a standard/reference samples; 20 head/20limb/20pubic;

where to look for prints

points of entry, directly around the crime, broken glass near window, door etc, light switches, door handles and locks, anything left by perpetrator

recording of the crime scene

precise note-taking is mandatory; record time call was received and arrival time and entrance times;

Francis Galton

published the first book on finger printing(1892) - statistical proof

line spectra

radiant energy may emit a single wavelength; one wavelength=monochromatic(laser); most radiation sources produce multiple wavelengths

infrared spectroscopy

radiation =12,800cm^-1 - 10cm^-1; divided into near, mid and far infrared radiation; near is measured with instruments similar to UV-visible; mid=fourier transform IR and is most commonly used; Uses monochromatic form of light; monitors radiations and vibrations; absorption in the infrared region of the spectra yield a much more complex pattern; different compound and how they are bonded varied the absorption

objective of the csi

reconstruct the incident(flawlessly); determine the sequence of events; determine the mode of operation; uncover the motive; determine if anything has been removed; determine what the criminal has done; recover physical evidence

photography unit

record and examine physical evidence; digital imaging (IR, UV and xray) makes invisible data visible

what to do until investigation team arrives

record names of witnesses; record names of people who have entered the scene; note who was initially at the scene; establish the facts; avoid suspect interaction with witnesses; avoid witnesses interacting; protect evidence

shoeprint image capture and retrieval(SICAR)

record of shoe print(scanned and digital); 1)reference file(known brands); 2)suspect file; 3)unknown file

nature of blood

refers to a complex mixture of cells, enzymes, proteins and inorganic substances

collecting wet blood samples

remove and place into paper bag; take to secure location and remove; allow to air dry thoroughly; repackage; if repackaged into new bag, old bag should also be packaged; package samples separately; dont expose to extreme heat or humidity

ridge characteristics

ridge dots, bifurcations, double bifurcation, opposed bifurcation, trifurcation, ridge endings, ridge crossing, enclosure, island, bridge, delta

striation marks

rows of parallel scratched; moving surface comes in contact with another surface

2D

rubber stamp evidence; flat images; a coated surface comes in contact with another surface(something on hand transferred to something else)

injured person on scene

saving lives=officer's #1 priority; judgement call is needed as to how severe the injury is; sketch a mental picture of how/where the injured person was found; look for evidence around the victim-hair, fibers etc; officer should arrange for custody of the injured person's clothing as evidence

can area of the body be determined?

scalp hair-has little diameter variation and a uniform pigment color; pubic hair-short and curly with a variety of shaft diameters and continuous medullae; facial hair-coarse, triangular in cross-section, and have blunt tips(shaving)

photographs should depict:

scene, entrance/exit paths potentially used by criminals, witnesses-people around(individuals, close ups, clothes), close ups-show detail(scale), evidence:location with respect to other objects, distances; must accurately show color, scale, form, relationship with other objects, distance

how does forensic evidence differ from other evidence?

scientific inquiry, applied techniques, the use of a wide variety of traditional natural sciences, proven reliability(low error)

dead person on the scene

seal off the scene, body should NOT be touched, use a hard wired phone to call for superior officer on duty/coroner(dont want media involved AT ALL) - media monitors police frequencies

types of plea strategies

self defense, the insanity defense, the influence of drugs or alcohol, the alibi defense, entrapment

serial number restoration

serial numbers are stamped into the metal with high force; criminals grind, rifle or punch out the serial number to avoid being tracked; the force of the stamped numbers extend below the punched area and have stressed the metal-use an etching material; stressed area dissolves, revealing the original numbers

various forms of impressions:

shoe, barefoot(class-unique), tire, fabric(unique-class), blood

Thin layer chromatography(TLC)

silica or aumina(inorganic) coated glass plate; cellulose coated glass plate(organic); spot sample onto plate with a capillary tube; place plate into developing chamber;

physical developer

silver based reagent; porous surfaces; good for items that have been wet

trace evidence

small or microscopic material

surface

smooth, textured surface dropped straight down

physical properties

something that can be observed or measured without changing the composition of the matter; appearance, texture, solubility, color, polarity, density, melting point etc...

cat medulla

spherical

types of searches

spiral, grid(sloped), strip or line search(flat), quadrant or zone search

deer medulla

stained glass spheres

paper chromatography

stationary support(cellulose paper); components move up the paper at different rates; rates are dependent on solubility and paper retention; visually see spots form on paper

video taping

still need photos, start at outer limit, narrate(speaker's name, date,time,case# etc); no others talking; no editing or erasing; scales of close up shots; pan in(relative location); photography isnt enough for adequate documentation;

Preservation of a crime scene

string off the scene; lock the door etc; blockade potential entry and exit paths;

what is forensics?

the application of science to the criminal justice system a connection with and used in some form of debate allows for a better criminal justice system

separation is based on

the distribution between 2 phases- mobile phase(solvent) and stationary phase(absorbent)

the movement of the compounds are dependent on

the driving forces of the mobile phase and on the retarding forces(absorption)

what does spectroscopy measure?

the intensity of radiation

height

the larger the crown, the higher the blood fell from on a constant surface

problem with fibers

the mass production of fabrics limits the value of fiber evidence; it is very unusual for fiber evidence to serve as an individual characteristic

rifling-lands

the original bore between two grooves

reflection

the return of light (bending back)

telogen

the root appears like a club; 2-6 month process; the hair is pushed out of the follicle(falls out)

forensic serology

the study of blood(antigen/antibody interactions); 1901-ABO; 1937-blood factors determined; Rh=rhesus antigen(protein)-if present(+) if not(-)

TLC

thin layer chromatography

fingerprint patterns

three groups: loops(65%), whorls(30%), archers(5%)

soft impressions

tire or shoe on a surface(earth); cast(class-1 dental stone); gypsum based; frame area; spray area with a wax and dry for 10 minutes; pour material; dry for a min of 30min; label case#, date, location and name; for snow - use latex

in a crime scene never:

touch or move anything at the scene(contamination), add anything to the crime scene(cause delays) --if something is altered, note the exacts

optional full service crime lab units

toxicology, latent fingerprinting unit, polygraph unit, voice-print analysis unit

specialized forensic scientist

trace, biological, reconstruction

basic forensic scientist(biology and chemistry)

trained in: recognition, identification, collection and preservation

locards exchange theory

transfer of hairs, fibers and other debris; when a person comes in contact with the environment, it is changed in someway; this transfer links the suspect to the scene

comparison microscope

two stereo or compound scopes bridged together; overlap images;

UV

ultraviolet spectroscopy

void

uniform patter where something blocked the blood spray

fingerprinting made easy

using a typical 12-13 point standard analysis, an algorithm is created and logged in a computer; fingerprint type, parts etc are identified; searched through AFIS: automated fingerprint identification system

metal jacket

usually copper

Tool marks

usually encountered with a burglary(breaking and entering); prying a window, door, safe; usually found on the frame or near the lock; usually an indentation is left behind; these impressions are usually class characteristics;

evidence beyond crime scene

victim's clothing, fingernail scrapings, head and pubic hairs, blood(dna), vaginal, oral, and anal swabs(rape), recovered bullets from a body, hand swabs from a shooting victim

the wave nature of light

visible; part of electromagnetic spectrum; carries energy through space; radiant energy; electromagnetic radiation travels at the speed of light(3x10^8m/s) ; up and down movement-peaks and troughs moving at regular intervals; the distance between two peaks or troughs= one wavelength; frequency= the number of complete cycles or wavelengths that pass a given point per second

UV-visible spectroscopy

wavelength region of 160-760nm; measuring the % transmittance or absorbance; when a wave encounters a molecule, the wave can either SCATTER or ABSORB; solutions are contained in a transparent cell; concentration is linearly related to absorbance; run a blank test first so that the sample ONLY is being studied

documenting the scene

well written notes; photographs; videotape(sounds); sketches

projected blood stains

when a force is exerted; arterial spurt; blood exiting under pressure

Scatter

when the direction of the wave is changed

Absorption

when the energy is transformed to the molecule