Chapter 2: Types of Evidence

1. Testimonial Evidence – statement made under oath by a competent witness Juries are heavily influenced by eyewitness accounts What might influence their accuracy? lighting, stress, brief encounter, distractions, time lapse between crime and questioning Memory errors are common

Points to consider: Victims of serious crimes have a more accurate memory of the event Adults have a better memory than children Witnesses remember actions better than descriptions Open ended questions get better answers Most cases of an innocent person being convicted were due to mistaken eyewitness identification

2. Physical Evidence - any object or material relevant in a crime More reliable than testimonial evidence Forensic scientists must determine the identity and origin of the physical evidence

Value of physical evidence: Can prove a crime was committed Ex: gasoline at a fire can prove arson Can support or refute testimony Ex: Was the blood from the suspect (as claimed) or from the victim Can link a suspect with a victim or crime scene Ex: pollen and soil in shoe tread match pollen and soil at crime scene

Can determine a person’s identity Ex: DNA or fingerprints Can allow investigators to reconstruct a crime Ex: Blood spatter may show relative positions

3. Circumstantial Evidence – implies a fact without proving it Blond hair in hand of murder victim implies murderer was blond Size 5 shoe print implies murderer wore size 5 Many people are blond, many wear size 5 – fewer are both blond and size 5 More evidence narrows the suspect pool

4. Individual Evidence – material that can be related to a single source 5. Class Evidence – material that can only be associated with a group of items that share characteristics