1. Evidence
Chapter 2

2. 2 types of evidence: Testimonial Evidence: Physical Evidence
Statement made under oath
Physical Evidence
Any object or material relevant in a crime
Tangible
Direct/Indirect
Class/Individual

3. Testimonial evidence:
Testified to under oath (usually in the court)
Studies show 80% conviction rate in cases with eyewitness.
Most known cases of wrongful conviction involved an eye witness.

5. Things that reduce accuracy of eye witness:
Length of time of encounter
Darkness/ distance
Stress: weapon diverts attention
Time between event and questioning
New info can affect memory
Read about case
Look at mug shots
Leading questions “was the offenders shirt red?” instead of “what was the offender wearing?”

7. Studies show: Witnesses are more accurate at noting suspects:
Sex
hair color
Witnesses are less accurate with noting suspects:
age, height, specific race
A witness is more accurate if suspect is physically similar to themselves

8. Make good witnesses: middle-aged Make poor witnesses:
Elderly
Young children
Alcohol or drug users
Head injury

10. Physical evidence: Can be direct or indirect Any object or material:
Microscopic: DNA, particles in soil
Macroscopic: hair, finger print, blood
odor

12. Physical Evidence can be used to:
Prove a crime was committed; gas at fire
Back up/refute witness testimony
Link suspect to crime scene; prints at scene
I.D. people that were there
Reconstruct the crime
In general, physical evidence is more reliable than testimonial evidence.

14. Known/Control sample:material that comes from a proven or known source
Questioned/Unknown sample: found at crime scene
Example: find fingerprint at crime scene, compare it with all KNOWN prints through AFIS.

15. Indirect evidence: Does not directly prove something
Physical evidence: strand of hair, car LIKE yours

16. Example:
Direct evidence: drugs on a person proves possession.

17. Example:
Indirect evidence: wad of money on person….suspect drug sales.

18. Circumstantial Evidence
Evidence based on suggestion rather than personal knowledge or observation, more you have, the better
Example: A blond hair is found in hand of a murder victim with black hair.
Circumstantial because there are many blonds.
If a footprint size 11 was also found, it is circumstantial
Put them together and you limit the pool of suspects

19. Individual vs. Class Evidence
Individual Evidence: evidence that can be traced to one source
DNA, fingerprints, broken glass or paper that fits like puzzle.
Class Evidence: can be classified into a group.
black hair, white shirt, denim pants

21. Does class evidence have any value?
What kind of evidence is most common?
Are most criminals smart?

23. The product rule:
The more class evidence you have the useful it becomes.

24. Probative value The worth/value of evidence in court
Example….soil or red paint on jeans not very valuable…..both on 1 pair of jeans and both match soil/paint at crime scene!

25. Probability Product rule for the probative value of class evidence.
Suspect wearing white shirt, blue pants, Light brown hair

26. Class to Whole population
How many kids in this class wearing white shirt
Say 10/30 =.333
Whole school population 1200
1200 x .333 = 400 kids in school wearing white shirt.

27. Sample population to whole
Blue pants
Say 15/30 in this class = .5
.5 x 1200 = 600 in the school wearing blue pants

28. Sample population Light brown hair 15/30 = .5
.5 x1200 = 600 students in school with light brown hair

29. Probative value
How do you estimate how many kids in the Whole school are wearing white shirts and blue pants and light brown hair

30. The Product Rule
.333 (1/3) of kids in this class are wearing white shirts.
.5 (1/2) of kids in this class are wearing blue pants
.5 (1/2) of kids in this class have light brown hair

31. The Product Rule
.333 x .5 x .5 = .0825
.0825 x 1200 = 100
Narrowed school population down to 100 possible suspects with all 3 criteria