1. Chapter 3 Physical Evidence

2. Any & all objects that:  establish a crime  link a crime to its victim  link a crime to its perpetrator Must be recognized at scene & preserved!!

3. Characteristics of Physical Evidence

4. Individual Characteristics Evidence that can be pinpointed to a specific source Fingerprints, DNA, bullet markings

5. Class Characteristics Evidence that can only be associated with a group and not a single source Fibers, hairs, blood type

6. Significance of Class Evidence Unfortunately, most evidence is class so for it to be valuable  find as much as possible As the # of objects , the probability of a person’s involvement  Evidence can also exclude or exonerate an individual

7. Types of Physical Evidence

8. 1. Blood, Semen, Saliva Liquid or dried Human or animal

9. 2. Documents Handwritten or typewritten Source or authenticity is determined Clues  Type of paper  Ink  Indented writings

10. 3. Drugs Street drugs (cocaine) Prescription ones too (painkillers) Sale, manufacture, distribution, & use

11. 4. Explosives Any device or object that might contain residues

12. 5. Fibers Natural (cotton) Synthetic (nylon) Locard’s Principle of Exchange

13. 6. Fingerprints Visible Plastic (impression) Latent (invisible)

14. 7. Firearms/Ammunition Guns Bullets  discharged or intact

15. 8. Glass Particles or fragments Windows with bullet holes

16. 9. Hairs Animal or human Species must be determined

17. 10. Impressions Tire marks Shoe prints Tracks Bite marks (food or skin) Glove & fiber impressions

18. 11. Paint Wet or dried Car accidents or hit-and-runs

19. 12. Powder Residues From firearm discharge Check clothing, sheets, & hands

20. 13. Petroleum Products Oil or grease stains Gasoline residues

21. 14. Tool Marks Such as from a hammer that was used in a murder

22. 15. Soil & Minerals Link a person to a certain location Often embedded in shoes Analyzed to tell if a body has been moved

23. Functions of the Crime Lab

24. Identification Determines the physical & chemical properties of a substance Analytical procedures must eliminate all but one substance

25. Comparison Determines whether 2 or more objects have a common origin Evidence is compared to standard or reference samples

26. Crime Scene Reconstruction

27. Pieces together events that occurred before, during, and after a crime Requires the help of:  law enforcement  medical examiner  criminalist (forensic scientist)