What is the value of physical evidence?

Class vs. Individual
Today’s Lesson Question:
What is the value of
physical evidence?
Today’s Objectives
Students will be able to:
1) distinguish between individual and
class evidence.
2) determine the significance of
class evidence.
Consider THIS!
Websites like amazon.com make
recommendations about things you
based on your previous purchases.
• How much can someone really tell
about your personality based on
the things you purchase?
• What information can be culled
from your garbage?
“Garbage-ology” Activity
• Each bag is partially filled with an
assortment of (non-organic)
waste: notes, bills, magazines,
newspapers, pictures, etc.
• Work in groups to analyze the
contents of garbage bags
• Complete the “Garbage-ology”
What Have We Learned?
Physical evidence
• Is part of "holy trinity" for solving
crimes -- physical evidence, witnesses,&
• Without one of the first two, there is
little chance of even finding a suspect.
• In homicide and sexual assault cases,
physical evidence is the number one
determinant of guilt or innocence.
• is also the number one provider of
extraordinary clearances, where police can
link different offenses at different times
and places with the same offender.
Class vs. Individual Evidence
• Individual Evidence
▫ The best evidence is anything that
can be linked to a unique, single,
specific source.
▫ Examples are fingerprints,
handwriting, DNA patterns, and
sometimes physical matches, such as a
piece of broken glass that exactly
fits to its mate (like a jigsaw
puzzle piece).
Class vs. Individual Evidence
• Class Evidence
▫ Most evidence has characteristics
common to a group of similar objects,
not to one single object.
▫ A way to increase the probative value
of class evidence is to find as many
different types of objects as
possible to link the suspect to the
crime or the victim.
Can This Evidence Be Individualized?
• There are 10 stations set up around
the classroom. At each station there
are one or more objects. Working in
teams of two, examine the object(s)
at each station.
• Complete the worksheet while you
examine each set of evidence.