3.1 & 3.2 Review Questions ANSWERS
1. List five examples of each of the following types of physical evidence
a. Biological materials – blood, saliva, semen, DNA, hair, organs, physiological fluids
b. Impressions – tire, shoe, depressions, tracks, glove, fabric impressions, tool marks,
bite marks
c. Manufactured items – firearms, ammunition, fibers, paint, glass, petroleum
products, plastic bags, rubber, polymers, vehicle headlights
2. Explain how the product rule is relevant to the murder conviction of Wayne Williams.
As the number of different objects linking an individual to a crime increases, the probability of
that person being involved increases dramatically.
28 fiber types linking him to several murder victims increases the likelihood that he was the
killer
3. What is the greatest weakness of class physical evidence? What is the main reason for this
weakness?
Cannot relate physical evidence to a common source with a high degree of certainty
Evidence possessing class characteristics can be associated only with a group and never a single
source
4. What is the greatest value of class physical evidence?
It has the ability to corroborate events with data in a manner that is, as nearly as possible, free
of human error and bias
5. Who ultimately determines the significance of physical evidence in a trial?
A. The judge
C. The supreme court
B. Expert witness
D. The jury
6. State 2 reasons why it is important to consider the relevance of scientific evidence before
allowing it to be introduced into a criminal case.
A) Physical evidence is accorded great weight during jury deliberations
B) Failure to take proper safeguards when determining the relevance of evidence may
unfairly prejudice a case against the accused
7. Why does a forensic scientist often opt not to use the most sensitive analytical techniques
when comparing suspect substances?
Carried to the extreme, no two things in this world are alike in every detail. Measurements that
are extremely sensitive may show differences between 2 samples that suggest the samples
came from different sources even though they actually came from the same source
8. How have IAFIS and CODIS aided criminal investigations?
Enables various organizations to electronically exchange and compare DNA profiles and
fingerprints.
Links crimes to each other and to convicted offenders