Chapter 2 Types of Evidence
Why Physical Evidence is Vauluable
1. Physical evidence can prove that a crime has been committed and set the scene for investigation; for example, gasoline at the scene of a fire may prove arson. 2. Can back up witness testimony or prove it false; for example, a forensic scientist can test a bloodstain that a subject claims is his own and not the victims 3. Can link a subject with a victim or with a crime scene; for example, a broken piece of headlight glass found in the cuff of a suspects pants could place him at the scene of a hit-and-run accident 4. Can determine the identity of people associated with a crime; for example, fingerprints, handwriting, or DNA might prove that a certain person was at a crime scene 5. Allows investigators to reconstruct a crime; for example. blood spatter patterns may show where the suspect and victim were locative relative to each other and indicate what happened and in what order
Factors when weighing an eyewitness account
1. Whether the witness already knew the accused , and what their relationship had been 2. How much time passed between the offense and the identification 3. whether the witness had already identified (or failed to identify) the defendant 4. whether the witness had already identified someone else
Common Types of Physical Evidence
Drugs and toxic substances, paints, gunshots and residues, firearms and ammunition, impressions, petroleum products, alcohols, rubber material, resins, plastics, explosive residues, serial numbers, documents, fibers, soil, glass, blood, body fluid, fingerprints, hair, tissues, pollen, wood material, feathers, bones, and tool marks
Circumstantial Evidence
Evidence based on suggestion rather than personal knowledge or observation
Indirect Evidence
Evidence providing only a basis for interference about the disputed act
Class Evidence
Material that can be associated only with a group of items that share properties or characteristics
Individual Evidence
Material that can be related to a single source; individualization always involves a comparison
Known or Control Sample
Material that comes from a proven or known source
Questioned or Unknown Sample
Material that has been collected from a known location but is unknown of origin
Evidence
Something that tends to establish or disprove a fact. Evidence can include documents, testimony, and other objects.
Physical Evidence
Tangible item that tend to prove some material fact; also called real evidence
Probative Value
The ability of evidence to prove something that is material to a crime
Testimonial Evidence
What is said in court by a competent witness; also called direct evidence or prima facie evidence