2. › Established “ Locard’s Exchange Principle ”- whenever 2 people/objects come into contact, materials will be exchanged between them. › Criminals contacting an object/person  cross-transfer of evidence.  You may find something of the criminal on the victim and vice versa.

3.  Intensity, duration, and nature of the materials in contact determine the extent of the transfer.  Ex: Fistfight vs. Brushing past each other

4.  Trace (or Transfer) Evidence - extremely small but measureable amounts of physical or biological material found at a crime scene.

5.  Briefly describe Locard’s principle of exchange.  Define trace evidence.

6.  As you watch the video clip about finding trace evidence: 1. Record information about the various methods and tools used in collecting trace evidence. 2. Identify the examples of trace evidence discussed in the video. **Information may appear on future tests/quizzes**  http://www.youtube.com/watch?v=Iy8sm1V0dk0&feature=share&list=CLcjn6SMEg4a8 http://www.youtube.com/watch?v=Iy8sm1V0dk0&feature=share&list=CLcjn6SMEg4a8

7.  While watching the video consider the following question: › How can trace evidence help solve a crime?  http://youtu.be/AMmSCXzmxD4 http://youtu.be/AMmSCXzmxD4

8.  Evidence that (if true) proves an alleged fact, such as an eyewitness account of a crime.

9.  Also known as indirect evidence  Evidence used to imply a fact but not prove it directly.

10.  Which major category of evidence (direct or circumstantial) do you think trace evidence falls under?

11. Answer the following question in your notebook:  Describe how trace evidence can be a critical element to solving a crime.

12.  Animal/human hair  Fingerprints  Soil or plant material (pollen)  Body fluids such as mucus, semen, saliva, or blood  Fiber or debris from clothing  Paint chips, broken glass, or chemicals such as drugs or explosives

13.  Individual evidence - narrows a suspect’s identity down to a SINGLE person or thing. › Evidence typically has unique characteristics that link it to only one person/thing.  Example: Fingerprints

14.  Class Evidence - narrows an identity to a group of persons or things. › Ex: ABO blood type of a sample of blood found at a crime scene.

15.  Circumstantial evidence can either be physical or biological in nature. › Physical evidence -  Often reduces the number of suspects to a specific, smaller group of individuals (exception being fingerprints).  Fingerprints, footprints/shoeprints, tire impressions, tool marks, fibers, weapons, bullets, and shell casings.

16. › Biological Evidence -  May make a group of suspects very small, or reduce it to a likely individual.  Body fluids, hair, plant parts, natural fibers.