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Chapter 3 – Physical Evidence I. Analysis of physical evidence Physical evidence is: Any or all objects that can establish that a crime has been committed or can provide a link between a crime and its victim, or a crime and its perpetrator; anything that is tangible, can be seen or measured, with or without magnification. Types: 1. Blood, semen, and saliva 2. Documents 3. Drugs 4. Explosives 5. Fibers 6. Fingerprints 7. Firearms and ammunition 8. Glass 9. Hair 10. Impressions (teeth, tools,…) 11. Organs and physiological fluids 12. Paint 13. Petroleum products 14. Plastic bags 15. Powder residues 16. Serial numbers 17. Soil and minerals 18. Tool marks 19. Vehicle lights 20. Wood and vegetative matter II. Two reasons to exam physical evidence 1. Identification – Source of physical evidence = body, crime scene, suspect 2. Comparison Characteristics: a. Individual: can be identified with a particular person or source (DNA; Fingerprints, random striations) b. Class: common to a group of objects or persons (Levi blue jeans; white paint, green carpet,…) III. The Significance of Physical Evidence A. Assessing the value of physical evidence. 1. Class evidence is not unique. 2. Can compare chemical and physical properties. 3. More than one type of class evidence can lead to extremely high certainty. B. Maintain Chain of Custody –continuity of possession of evidence; adhere to standard procedures in recording the location of evidence, marking it for identification, and properly completing evidence submission forms for lab analysis. EVERY person who handled or examined the evidence MUST be accounted for. Physical evidence is accorded great weight by juries and scientists are held in high esteem so great care must be given to make sure that scientific evidence is not handled inappropriately and therefore give doubt in the case. IV. Forensic Databases A. Fingerprint Databases – IAFIS (Integrated Automated Fingerprint Identification System). A national fingerprint and criminal history system maintained by the FBI. Started in 1999, now has 50 million subjects and 500 million fingerprint images. B. DNA Databases – 1998, FBI’s Combined DNA Index System (CODIS). The forensic index contains about 110,000 profiles from unsolved crime-scene evidence; the offender index contains the profiles of 7 million convicted or arrested individuals. In a typical month, matches are found linking suspects to 26 murders, 57 rapes, and 3000 motor vehicle, property and drug crimes.