1. Criminalistics (Saferstein)
Physical Evidence
Criminalistics (Saferstein)
Chapter 3

2. Definition of “evidence”
"Anything which is legally submitted to a competent tribunal as a means of ascertaining the truth of any alleged matter of fact under investigation before it"

3. Types of evidence Direct evidence
"That which (if true) proves the fact in dispute ... in the case of a witness...it is the result of personal knowledge derived through one or more of the five senses"

4. Types of evidence Indirect or circumstantial evidence
"That which (if true) tends to establish an issue in dispute by proving another fact...[it] does not conclusively establish that issue, but causes an inference or presumption of its existence"

5. Types of evidence Real or physical evidence
May include almost any (tangible) object...that is directly linked to crime charged and may be observed by a judge and /or jury
Circumstantial physical evidence
Example: Witness testimony that an accused was known to own a revolver of the same make and caliber of that used in the commission of a homicide.

6. Types of evidence Testimonial evidence
"That which is supplied through the verbal testimony of a witness (or suspect)"
Circumstantial testimonial evidence
Example: The perpetrator of a crime was observed wearing a red shirt with vertical blue stripes; the individual accused of the crime owns such a shirt.

7. Value of physical evidence
Physical Evidence Versus Testimonial Evidence
Human factor
Physical evidence "can't lie, quit, die, forget, or get fired"
Testimonial evidence may change or source may become "nonexistent' between original and court version
Physical properties
Cannot change
Only interpretation can change or be in error

8. Value of physical evidence
Circumstantial Variability
If the item of physical evidence is found and subsequently associated with a suspect where the suspect had no right to be, then (when identified) the evidence may:
Establish a suspect's presence at the crime scene.
Establish probable cause.
Establish proof beyond a reasonable doubt.
If the time of physical evidence is found where a suspect may have had a legitimate right to be (innocent access), then the evidence may:
Have no significance.
Provide leads to follow to establish the case via other sources.

9. Class characteristics
a. Describe the physical object and limit (but not eliminate) the likelihood that similar objects exist.
b. The greater the number of class characteristics that can be associated with a given object, the smaller the category within which the object can be placed.
c. The larger the number of class characteristics, the greater the value in an investigation.
d. Physical evidence with class characteristics may have more than one possible source.

10. Individual characteristics
Individual/Identification Characteristics of Physical Evidence
a. Establish a physical object's difference/uniqueness from all others within its group.
b. Establish the unique identity of an object or its source to the exclusion of all others.
c. Examples:
(1) Fingerprint impressions
(2) DNA analysis
(3) Ballistic examinations
(4) Footwear/tire impressions

11. Mathematical Probability
The probability of any given occurrence at a specific place or time relates to the value of a piece of physical evidence. 

12. Example 1:
Examples:
1969 yellow VW Beetle is observed in commission of a hit and run in  1969.
In 1969, yellow VW Beetles were common (popular car, limited color selection). The chances were greater that two yellow 1969 VW Beetles could exist in the same vicinity in 1969 than today. Therefore, this information may lack significance in 1969.

13. Example 2:
1969 yellow VW Beetle is observed in commission of a hit and run in 2011.
1969 yellow VW's (and VW's in general) are less common in Therefore, the rate of occurrence of the presence of a yellow VW Beetle would be significantly less. Thus, the odds (mathematical probability) would favor such a vehicle being the suspect vehicle if found in the vicinity/jurisdiction where the hit and run occurred. The presence of fresh damage would also impact the odds.

14. Theory of Transfer/Exchange
a. "When two objects touch each other, trace substances of each are exchanged."
b. When a suspect enters a crime scene, he/she leaves something behind and/or takes something away from the scene.
c. This provides an opportunity to link suspect with the scene/crime providing proper collections/examinations are made from/of scene/victim/suspect.

15. Major Groupings Of Physical Evidence
a. Physical evidence is any material, however microscopic, solid, liquid or gaseous, that may aid in the determination of the truth during the investigation of a crime.
b. Physical evidence capable of scientific analysis that is likely to be found at the scene of a crime falls into eight (8) major groups and one (1) miscellaneous group.

16. Groups of physical evidence
(1) Weapons - I.D.
(2) Blood, saliva, and semen - I.D.
(3) Latent impressions - I.D.
(4) Shoe and tire impressions - I.D.
(5) Tool Marks - I.D.
(6) Questioned documents - Class to I.D.
(7) Soil - Class
(8) Glass - Class
(9) Miscellaneous trace evidence such as hair, fibers, paint chips, and  bomb residue - Class

17. Point of entry Physical Evidence - Point of Entry
a. Subject tends to be nervous and in a hurry at this point and is often somewhat careless.
b. Physical evidence to look for at the point of entry.

18. b. Physical evidence to look for at the point of entry.
Trace fibers/prints from subject’s clothing/gloves
Blood (breaking glass often causes cuts.)
Tool marks
Hairs
Splintered wood
Chipped paint
Broken glass (inside/outside)
Latent prints (finger/palm)
Footprints (inside and outside)
Discarded items/tools