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Physical Evidence

Physical Evidence. Chapter 3. Types of Physical Evidence. Blood, semen, saliva Document Drugs Explosives Fibers Fingerprints Firearms and ammunitions Glass Hair http:// www.youtube.com/watch?v =Wo-VO4sAJI4&feature=related. Impressions Organs and fluids Paint Petroleum products

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Physical Evidence

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  1. Physical Evidence Chapter 3

  2. Types of Physical Evidence • Blood, semen, saliva • Document • Drugs • Explosives • Fibers • Fingerprints • Firearms and ammunitions • Glass • Hair • http://www.youtube.com/watch?v=Wo-VO4sAJI4&feature=related • Impressions • Organs and fluids • Paint • Petroleum products • Plastic bags • Plastic, rubber, polymers • Powder residues • Serial numbers • Soil and minerals • Tool marks • Vehicle lights • Wood and vegetative matter

  3. Analyzing Physical Evidence • Identification—process of identifying the physical or chemical identity of an unknown substance • Comparison—process of deciding whether two or more substances have a common origin

  4. Identification • Check for presence of illicit drugs • Presence of gasoline in explosives • Step 1—use of standard testing procedures • Step 2—do as many tests as necessary to exclude other possibilities

  5. Comparison • Subject suspect specimen and known standard to same battery of tests • Step 1—Test various qualities of test and standard subjects • Step2—Draw conclusions about the origins of the specimens

  6. Comparison testing continued • Individual characteristics—properties of evidence that can be attributed to a single source with a high degree of certainty • Class characteristics—properties of evidence that can only be associated with a group and never with a single source

  7. Value and Limitations of Physical Evidence • Value • Needs to corroborate data without introducing error or bias • Collective class evidence can be very conclusive in courtroom • Limitations • Jury or judge determines value in courtroom • No two things are completely identical if all exhaustive tests are looked at

  8. Forensic Databases • Suspects can be linked to a crime through comparative analysis • Requires suspect to match to known standards • Link information of all 50 states and other nations

  9. Fingerprint Database • Integrated Automated Fingerprint Identification System (IAFIS), national fingerprint system maintained by the FBI and launched in 1999 • Comparison search from anywhere in US can be done in just minutes • Other countries have similar national systems • http://www.youtube.com/watch?v=pSwH-51OFEQ

  10. DNA Database • Combined DNA Index System (CODIS) by FBI became fully operational in 1998 • National collection of DNA from two sources: forensic index and offender index • Forensic index—DNA collected from physical evidence • Offender index—DNA from past offenders • http://www.youtube.com/watch?v=Trdu_s_XzRo

  11. Other Databases • National Integrated Ballistics Information Network (NIBIN) allows comparison of markings made by bullets and firearms • International Forensic Automotive Paint Data Query (PDQ) contains data for color and paint information for original automotive paints • Shoeprint Image Capture and Retrieval (SICAR) is not government regulated—it is used to compare and identify crime scene shoeprints

  12. Crime Scene Reconstruction • Method used to support likely sequence of events at crime scene by observing and evaluating physical evidence and statements made by those involved with the incident • http://www.youtube.com/watch?v=HS67MGEaGRM • Involves several personnel • Medical Examiners—cause of death, movement of body, etc • Criminalistics—use lasers to find path of gunfire, angles, positions of shooters, etc. • Law Enforcement Personnel • http://www.youtube.com/watch?v=e3E2AMgDf5Y

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