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