1. Locard’s Exchange Principle
“When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur.”

2. Trace Evidence
Small but measurable amounts of physical or biological material found at a crime scene

3. Examples of trace evidence
Human hair
Animal hair
Fibers
Soil or plant material (pollen)
fingerprints
Body fluids (semen, blood, saliva, mucus)
Paint chips
Broken glass
Chemical residue

4. Types of Evidence
Direct: firsthand observations (eyewitness account, video camera, confessions)
Circumstantial: indirect evidence; implies a fact, but not directly prove it
Physical – bullets, weapons, impressions
Biological – body fluids, plant parts, hair
Trace evidence

5. Categories of Evidence
Class Evidence
Narrows identity to a group of persons or things
Example: blood type
Individual Evidence
Narrow identity to a single person or thing
Example: fingerprint

6. Crime Scene Evidence Direct or circumstantial evidence?
Physical or biological evidence?
Class or individual evidence?