Chapter 2: Types of Evidence
TYPES OF EVIDENCE
•Testimonial
-Statement made under oath.
-Given by a witness.
•Eyewitness
- “Perception is reality”
Physical (Indirect): Any object or material that is relevant in a crime.
•Direct Physical Evidence: Can prove an event.
-Possession of a controlled substance
-Alcohol content of blood
•Indirect Physical Evidence: Supports an event
-Presence of a blond hair
-A skid mark
Value of Physical Evidence
1. More reliable than testimonial
2. Proves a crime has been committed
3. Corroborates or refutes testimony
4. Links a suspect with a victim or with a crime scene
5. Establishes the identity of persons associated with a crime.
6. Allows the reconstruction of events of a crime.
Probative Value
1. Legally, the level at which evidence provides proof of the crime.
2. The probative value of individualized evidence is greater than that of class evidence.
•The value of probative evidence depends on probability.
Product rule:
-Used to determine the probability of a set of circumstances occurring in a specific situation.
Associative Value
•Used to place a suspect at a crime.
•The associative value of a suspect’s DNA at the crime scene is greater than that of fiber’s from the suspect’s cotton shirt.
Types of Physical Evidence
1. Transient Evidence:
A. Temporary; easily changed or lost; usually observed by the first officer at the scene.
B. Examples:
1. Odor 2. Temperature 3. Imprints and indentations 4. Markings
2. Pattern Evidence:
A. Produced by direct contact between a person and an object or between two objects
B. Examples:
1. Blood spatter 2. Gun powder residue
3. Tire marks or skid marks 4. Footprints
3. Conditional Evidence:
A. Produced by a specific event or action.
B. Examples:
1. Light 2. Fire 3. Location
4. Transfer Evidence:
A. Produced by contact between person(s) or object(s), or between person(s) and person(s)
5. Associative Evidence:
A. Items that may associate a victim or suspect with a scene or each other; ie, personal belongings
Classification ofEvidence by Nature
Evidence may also be classified based on its nature.
Biological
blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical
Chemical
fibers, glass, soil, gunpowder, metal, mineral, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer
Physical
fingerprints, footprints, shoe prints, handwriting, firearms, tire marks, tool marks, typewriting
Classifying Characteristics
Class:
Common to a group of objects or persons.
Individual:
Identified with a particular person or a single source
Class Evidence Examples
• Single layered paint
• Soil
• Glass fragments too small to fit together again
• Hairs / fibers
• Blood type
Individualization of Evidence
Process of linking evidence to a common source:
1. A person
2. A place
3. An object
Individualization requires that evidence be unique and connected to the common source without exception.
Individual Evidence Examples
1. The matching ridge characteristics of two fingerprints.
2. The comparison of random striation markings on bullets or tool marks.
3. The comparison of irregular and random wear patterns in tire or footwear impressions.
4. The comparison of handwriting characteristics
5. The fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle
Forensic Investigations
1. Recognition:
Ability to distinguish important evidence from unrelated material
2. Preservation:
Collection and proper preservation of evidence
3. Identification:
Use of scientific testing
4. Comparison:
Class characteristics are measured against those of known standards or controls.
5. Individualization:
Demonstrating that the sample is unique, even among members of the same class.
6. Interpretation:
Gives meaning to all the information.
7. Reconstruction:
Reconstructs the events of the case.
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