1. Evidence
Chapters 3 & 8

2. Types of Evidence
2 types exist
Testimonial
Physical

3. Testimonial Evidence Statement made under oath
Known as direct evidence
AKA Prima Facie evidence

4. Reliability of Eyewitnesses
Factors that can help or hurt your case
Nature of the offense and the situation in which the crime is observed
Characteristics of the witness
Manner in which the information is retrieved
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

5. Eyewitness
A police composite may be developed from the witness by forensic artist or a computer program
As a result of the influences in eyewitness memory, physical evidence becomes critical.

6. Physical Evidence
Impossible to list ALL objects that can be found at a crime scene
Remember, physical evidence can be ANYTHING

7. Common Types of Physical Evidence
Blood
Semen
Saliva
Documents
Drugs
Explosives
Fibers
Fingerprints
Firearms and ammunition
Soil and minerals
Vehicle lights
Glass
Hair
Impression
Organs
Petroleum products
Plastic bags
Plastic, rubber, and other polymers
Powder residue
Serial numbers
Wood and other vegetative matter

8. Types of Physical Evidence
5 types exist
Transient
Pattern
Conditional
Transfer
Associative

9. Transient Evidence
Is temporary evidence; can be changed or lost; usually observed by the first officer at the scene
Examples
Odor- perfume, gas, urine, cigarette
Temperature- surroundings, coffee, water, dead body
Imprints and indentations- footprints, teeth marks, tire marks
Markings

10. Pattern Evidence
Produced by direct contact between a person and an object or between two objects
Examples
Blood spatter
Glass fracture
Fire burn pattern
Tire marks
Gun powder residue
Body position
Tool marks
Furniture position
Projectile trajectory

11. Conditional Evidence Produced by a specific event or action Examples
Light- lighting conditions
Smoke- color, direction of travel, density, odor
Fire- color and direction, speed of spread, temperature and condition of fire
Location- injuries or wounds, bloodstain, victim’s vehicle, weapons, broken glass
Vehicles- doors locked or unlocked, windows opened or closed
Body- position, types of wounds; rigor, livor, and algor mortis
Scene- condition of furniture, doors and windows, signs of struggle

12. Transfer Evidence
Produced by contact between person(s) or object(s), or between person(s) and person(s)
Examples
Fingerprints
Hair
Fibers

13. Associative Evidence
Items that may associate a victim or suspect with a scene
Examples
Suspect has victim’s credit card or watch

14. Classification of Evidence by Nature
4 classifications
Biological
Blood, semen, saliva, sweat, tears, hair
Chemical
Fibers, glass, soil, gunpowder, metal
Physical
Fingerprints, footprints, shoe prints, handwriting
Miscellaneous
Voice analysis, polygraph, vehicle identification

15. Value of Physical Evidence
Generally more reliable than testimonial
Can prove that a crime has been committed
Can corroborate or refute testimony
Can link a suspect with a victim or with a crime scene
Can establish the identity of persons associated with the crime
Can allow reconstruction of events of a crime

16. Forensic Investigations
Includes some or all of the seven major activities
Recognition- ability to distinguish important evidence from unrelated material
Pattern recognition
Physical property observation
Information analysis
Field testing
Preservation- collection and proper preservation of evidence

17. Forensic Investigations
Identification- use of scientific testing
Physical properties
Chemical properties
Morphological properties
Biological properties
Comparison- class characteristics are measured against those of known standards or controls; if all measurements are equal, then the two samples may be considered to have come from the same source or origin

18. Forensic Investigations
Individualization- demonstrating that the sample is unique, even among members of the same class
Interpretation- gives meaning to all the information
Reconstruction- reconstructs the events of the case
Inductive and deductive logic
Statistical data
Pattern analysis
Results of laboratory analysis

19. Common Types of Identification
Crime labs may be requested to identify the following
Chemical composition of illicit drugs
Gasoline in residues
Nature of explosive residues
Blood, semen, hair, or wood
Blood has to be identified as human vs. other animal

20. Classifying Characteristics
2 types of characteristics
Individual
Evidence that can be associated with an extremely high degree of probability
Example- each gun makes a different impression on the bullet when fired
Class
Evidence associated only with a group
Example- blood types

21. Class vs Individual
These fibers are class evidence; there is no way to determine if they came from this garment
The large piece of glass fits exactly to the bottle; it is individual evidence

22. Role of Probability
Important in ascertaining the origins of 2 or more specimens
It is the frequency of occurrence of an event

23. Example- Bad
Suppose a crime took place in which the suspect left blood behind. The forensic scientist determined that the suspect has type A blood. Any person brought in and whose blood type was also A cannot be arrested on that ground because over ¼ of the population have that blood type.

24. Example- Good
Suppose a crime took place in which the suspect left saliva behind. The forensic scientist did a DNA analysis of the saliva and came up with a match to the actual suspect.