Criminalistics 440 Final

criminalist

scientist who studies forensic evidence

forensic specialists

photographs, latent prints, sketching, evidence collection, suspect processing, comparisons, report writing, courtroom testimony

CSI effect

the influence that crime shows such as CSI have on the public's perception of forensic science.

Edmond Locard

Locard's exchange principle: every contact leaves a trace

Basic prinicple of forensic science

Linkage Triangle

Victim, suspect, scene

firearms/toolmarks

unit looks at funcitonality, comparisons, distance determination, serial number restorations

trace evidence

paint chips, hair fiber, gsr, ignitable fluids

Match

2 objects that you are trying to determine if they originated from the same object

forensic chemistry

forensic alcohol + toxicology ante and postmortem

testimonial evidence

verbal or written statements provided by the victim, suspect, or eyewitness

can provide an understanding for motive or assist in explaining elements of a crime, subjective

documentary evidence

documents a crime, surveillance, photos, tape recording, emails

physical evidence

"real evidence" hair, fibersm friction ridge details, biological materials, tire impressions

- establishes who, what, when, where

class characteristics

Properties of evidence that can be associated only with a group and never with a single source.

random characteristics

characteristics unique to the item of evidence, can be directly associated to a specifc source

Basic actions of crime scene processing

assessing, observing, documenting, searching, collectiong, processing/analyzing

arrival to crime scene

10-97

Meet with officer

Major crime scenes have entry log

Assessing

Assessment is consistently employed throughout processing, assessing secondary scene, necessary equipment, additional personnel, lighting conditions, transitory evidence

Observing

Written notes are taken, photographs, videography, crime scene sketching, crime scene report

Searching

intrusive, will change state of the scene

secure all physical evidence is located, documented, collected

- zone, inward spiral, line, grid searches

Collection

Do not collect until documented, if there is a need to go out of sequence it needs to be written in the nites

PROPER collection to preserve integrity

Processing/analyzing

consider if collecting an item of evidence would yield better processing results back at station or crime lab

intrusive process

Departure

10-98

ISO

higher = brighter

how sensitive the camera's sensor to lighting is

Shutter speed

how fast the shutter opens and closes, determines the amount of light and motion blur

slower = no motion

higher shutter speed - lots of motion

Aperture

opening of lens thru which light passes

wide = low depth of field, more light

small = less light, greater depth of field

depth of field

what is in focus from foreground to background

overall photograph

depict general condition or layout of crime scene or evidence

incorporates landmarks

taken from 4 corners, should be overlapping

mid range photograph

evidence establishing relationships to others

close up photographs

every detail of evidence, entire subject is in focus, pictures with and without scale

crime scene sketch

serves to document layout, orientation, spatial relationships

not drawn to scale

PHOTOGRAPHS FIRST

birdseye sketch

most common, aerial view

only horizontal evidence

elevation sketch

verical surface like bullet holes, spatter, shoeprint

exploded sketch

floor folded down, vertical walls

to see spatial awareness on both horizonal and verical surfaces

perspective sketch

3d, most realistic

basic elements of a crime scene sketch

heading/block: name, date, case #, location, description of scene

diagram area: drawing graphically, showing scene and evidence

legend: defines various labels used in the sketch

orientation: N

scale: include for reference if one isn't used say "not to scale"

reference points: stationary objects to measure from

crime scene mapping

overall documentation of the size of the crime scene

items of evidence must be fixed

several methods, best depends on the circumstances

rectangular coordinates

easiest for indoors

well defined boundaries

evidence fixed by measuring at a right angle

2 measurements are taken at 90 to cetner of mass of item of evidence

triangulation coordinates

most effective for fixing

2 or 4 measurements from 2 distinct points of item of evidence

regular shaped item, use 4 points

irregular use 2 points

station line / baseline coordinates

measuring tape extended out along cardinal direction and measurements are made from evidence to baseline at right angles

crime scene report writing

do no use "we"

no hearsay

no speculation

info to include:

synopsis, scene preservation, lighting conditions, environmental conditions, actions, chain of custody

1st section of report

date and time of investigation, time of arrival, type of crime, location, contact person

2nd section of report

observation of the crime scene

3rd section of report

actions (photos, developing prints, swabs)

evidence collection

may change due to particular circumstances, collection of evidence if one of the last steps

improper collection can compromise future analysis

wear gloves and change between collecting each item of evidence

never use plastic (unless arson)

sharp object collection

put inside cardboard box, syringes should be placed in a plstic container made specifically for sharps

handguns/longgun collections

proper box based on size

zip ties can be used to secure

ammo should not be packaged

direction of muzzle noted on outside of box

toolmark analysis

vehicles, businesses, residences

bitemark evidence

photograph bite mark prior to swabbing or casting

if impression deep enough use microsil or silicone

shoeprint impressions

always take photographs of shoeprint impressions prior to collecting a cast or lift of the shoeprint

2-d ] lift

gel lift for most surfaces (oil, grease, dirt)

conventional black powder

electrostatic dust lifter for shoeprints on cloth, carpet

3-d lift

cast of shoeprint using dental stone, cast stone, plaster

electrostatic dust lifter

A device that operates by charging a plastic film, placed over the dust print, which creates electrostatic adhesions and draws the film onto the surface bearing the print. The dust particles are attracted to the film because of this charge and adhere to it.

dental stone

2lbs to 11 ounces water

stir 3-4 mins

30 min dry

24-48 hours done

paint

primer layer: adhesion to surface to protects against corresion

basecoat: contains pigments for color

topcoat/cleacoat: provides glossy finish and protection

collection of paint

wet: do not swab, use tongue depressor or plastic

dry: dependent on surface - cut/scrape paint

packaging: if on stick/plastic - wax paper

if dry: manilla envelope

hair layers

-Cuticle (outermost layer made of keratin)

-Cortex (middle layer with hard keratin for stiffness) pigment

-Medulla (core with flexible soft keratin)

human and animal hair

diameter of medulla/diameter of hair

humans = less than 1/3

fiber analysis

natural/manufactured

examiens chemical fingerprint of questioned fiber

use tweezers, tape lifts

gunshot residue

inorganic compounds of lead, barium, antimony, often found on shooter, hands, sclothing

striations

fine lines found in interior of barrel of gun

markings of firearms

firing pin, breech face, extractor, ejector

serial # restoration

usually stamped on a metal body or frame or plate

use chemical etching

distance determination (firearm)

when firearm is discharged, unburned, and partially burned particles of GP in additon to smoke are propeled out of barrel along with the bullet towards target

inked print

known print, exemplar

patent print

visible to the eye

factors affecting fingerprint ridge deposit

amount of contact/time

condition of object

environment

Cyanoacrylate fuming

Chemical treatment that utilizes superglue vaporization to produce a permanent white print. Amino acid reactions

Ninhydrin

A chemical reagent used to develop latent fingerprints on porous materials by reacting with amino acids in perspiration

Amido Black

protein dye stain that can develop faint bloody fingerprints on porous and nonporous surfaces

Small Particle Reagent (SPR)

A chemical used to process wet or greasy items for latent fingerprints, adheres to fats

processing tape

LCR, wet dye stain on adhesive

Wetwop

a special pre-mixed liquid formula that is designed to lift latent prints on the sticky sides of adhesive surfaces (i.e. most kinds of tape)

collection of touch/trace evidence

if dry, moisten cotton swab with 2 drops of sterile water

place in coin envelope

influences on trajectory

gravity, air resistance, muzzle velocity, angle of elevation, humidity, bullet shape, barrel length

vertical angle (trajectory)

angle at which a projective travels below or above a horizontal plane (positive and negative direction)

azimuth angle

horizontal angle between trajectory and fixed reference direction

evidence at autopsy

Trace evidence

Fingernail scrapings

Sexual assault swabs

Overlays ofwounds/patterns

Clothing

Muscle standards

Insects

minutiae

bifurcations, ridge endings, dots, enclosures

exposure triangle

iso, aperature, shutter speed

distance determination

farther away=less gunpowder

measurement used for bloodstains

mms

ejector marking

cartridge case thrown from the firearm breechface

The context of evidence can manifest itself in numerous ways. According to Rynearson and Chisum, these manifestations can be classified into five (5) categories. Which of the following is not a category?

-unpredictable effects

- functional details

- predictable details

- rational details

rational details