Unit 2: Evidence

1. Unit 2: Evidence 2.1 Types of Evidence

2. Locard’s Exchange Principle • There is always a cross transfer of evidence between suspect and victim or location. Ex: bat and the victim, vehicle and victim,

3. Classification ofEvidence by Nature • Biological: blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical.

4. Chemical: fibers, glass, soil, gunpowder, metal, mineral, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer.

5. Physical: fingerprints, footprints, shoe prints, handwriting, firearms, tire marks, tool marks, typewriting.

6. Miscellaneous: laundry marks, voice analysis, polygraph, photography, stress evaluation, vehicle identification

7. Direct vs Indirect Direct evidence: • establishes a fact • does not make any inferences Ex: • eyewitness accounts • confessions Indirect evidence: (aka circumstantial) • implies a fact or event without actually proving it • most forensic evidence is circumstantial Ex: • hair • foot print

8. Types of Evidence Two general types: • Direct (Testimonial)—a statement made under oath; also known as direct evidence or Prima Facie evidence • Indirect (Physical)—any object or material that is relevant in a crime; also known as indirect evidence. Examples are hair, fiber, fingerprints, documents, blood, soil, drugs, tool marks, impressions, glass.

9. Reliability of Eyewitness Factors: • Nature of the offense and the situation in which the crime is observed • Characteristics of the witness • Manner in which the information is retrieved Additional factors: • Witness’s prior relationship with the accused • Length of time between the offense and the identification • Any prior identification or failure to identify the defendant • Any prior identification of a person other than the defendant by the eyewitness

10. Eyewitness • A police composite may be developed from the witness testimony by a computer program or forensic artist. • “Perception is reality.” • As a result of the influences in eyewitness memory, physical evidence becomes critical. Faces—a composite program by InterQuest

11. Probative Value • The ability of evidence to prove something that is material (important) to a crime. Let’s take a look at some examples:

12. Evidence Example #1 • What is this object and what probative value might it have?

13. Evidence Example #2 • What is this object and what probative value might it have?