Download Chapter 3 – Physical Evidence I. Analysis of physical evidence

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts
no text concepts found
Chapter 3 – Physical Evidence
I. Analysis of physical evidence
Physical evidence is: Any or all objects that can establish that
a crime has been committed or can provide a link between a
crime and its victim, or a crime and its perpetrator; anything
that is tangible, can be seen or measured, with or without
1. Blood, semen, and saliva
2. Documents
3. Drugs
4. Explosives
5. Fibers
6. Fingerprints
7. Firearms and ammunition
8. Glass
9. Hair
Impressions (teeth,
Organs and
physiological fluids
Petroleum products
Plastic bags
Powder residues
Serial numbers
Soil and minerals
Tool marks
Vehicle lights
Wood and vegetative
II. Two reasons to exam physical evidence 1. Identification – Source of physical evidence = body, crime
scene, suspect
2. Comparison
a. Individual: can be identified with a particular
person or source (DNA; Fingerprints, random
b. Class: common to a group of objects or
persons (Levi blue jeans; white paint, green
III. The Significance of Physical Evidence
A. Assessing the value of physical evidence.
1. Class evidence is not unique.
2. Can compare chemical and physical properties.
3. More than one type of class evidence can lead to
extremely high certainty.
B. Maintain Chain of Custody –continuity of possession
of evidence; adhere to standard procedures in recording the
location of evidence, marking it for identification, and properly
completing evidence submission forms for lab analysis. EVERY
person who handled or examined the evidence MUST be
accounted for.
Physical evidence is accorded great weight by juries and
scientists are held in high esteem so great care must be given
to make sure that scientific evidence is not handled
inappropriately and therefore give doubt in the case.
IV. Forensic Databases
A. Fingerprint Databases – IAFIS (Integrated Automated
Fingerprint Identification System). A national fingerprint and
criminal history system maintained by the FBI. Started in 1999,
now has 50 million subjects and 500 million fingerprint images.
B. DNA Databases – 1998, FBI’s Combined DNA Index System
(CODIS). The forensic index contains about 110,000 profiles from
unsolved crime-scene evidence; the offender index contains the
profiles of 7 million convicted or arrested individuals. In a typical
month, matches are found linking suspects to 26 murders, 57
rapes, and 3000 motor vehicle, property and drug crimes.