Evidence Forensics 3

Definition of Evidence Anything legally submitted to a court of law that helps ascertain the truth of the matter under investigation The most important concept in criminalistics is identification (or individualization) of evidence

Purpose of Evidence To connect or eliminate suspects To develop or identify suspects To develop or show a similar method of operation To identify stolen items or illegal materials To prove or disprove an alibi To provide leads

The “Holy Trinity” of Evidence Physical evidence Most important determinant in producing a conviction Witnesses Confessions Without one of the first two in particular, it is very difficult to even find a suspect

4 Main Types of Evidence Testimonial Evidence presented by witnesses speaking under oath Physical Tangible objects found at a crime scene, etc. Sometimes hidden to plain view and only becomes apparent after scientific processes…referred to as “latent” Documentary Video, sound or audio recordings Demonstrative Objects, etc. used to demonstrate or recreate a tangible event, place or object Includes models, recreations, etc.

Testimonial Evidence People often remember more details from more severe crimes Sex, hair color, ethnicity “Reliable” witnesses Children and elderly – often not reliable Learning disabled, mental disabilities, drugs/alcohol How was information gathered? Open ended questions often yield best results “Was the person’s shirt red?” – NO!

Testimonial Evidence Other Factors Relation to people involved in crime Fear Prior incidents Personal trauma

Physical Evidence Transient Temporary, easily changed or lost Pattern Produced by direct contact Conditional Produced by a specific event or action Transfer Produced by contact between persons or objects Associative Items associated with a victim/suspect of scene

Transient Evidence Odors Temperature Imprints/indentations Markings

Pattern Evidence Blood spatter Glass fractures Fire burn patterns Ballistic trajectories GSR Body position Tool marks

Conditional Evidence Lighting – Lighting conditions Smoke – Color, direction of travel Location of injuries, positions, debris Vehicles – Doors locked/unlocked Body – Position, rigor/livor mortis Scene – Conditions/position of furniture

Forensics and Evidence Seven major activities in evidence use Recognition Preservation Identification (scientific) Comparison Individualization Interpretation Reconstruction

Legality of Evidence Chain of Custody Of highest importance to any investigation Shows the unbroken sequence of events that is caused by an item of evidence from the time it is found at the crime scene to the time it appears in court Every link must be documented from discovery, to gathering, storage, lab analysis, return to storage and transfer to court Include dates, times, people involved and what was done to the evidence If a constant chain can not be established, the evidence is worthless

“Standards of Admissibility” Vary from state to state, and sometimes from court to court within states Relevancy test Frye Standard 1923 In order for a scientific technique to be admissible, it must be “generally accepted” Now superseded by Daubert Standard Involved a polygraph test

“Standards of Admissibility” Coppolino Standard 1968 Allows for new types of tests to be used if adequate science exists Marx Standard 1975 Courts do not have to sacrifice common sense when evaluating scientific evidence Daubert Standard 1993 Court must decide on “expert” witnesses and general admissibility of evidence or techniques

Evidence Concepts Identity vs. Match Identity is a set of characteristics by which something(body) is known. Match is a set of characteristics that point to only one object/individual Class vs. Individual Class characteristics are common to a group of similar objects (e.g. Nike “swoosh”) Individual characteristics are unique to one particular item or individual

Science of Evidence Locard’s Exchange Principle States that each time an individual comes in contact with another, something of that individual is left behind while something of that place is taken away with the individual Hair, skin flakes, dirt, etc. can all be used to link someone to a location Evidence processing is expensive