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THREE

THREE. Physical Evidence. LEARNING OBJECTIVES. Distinguish between class and individual characteristics. Outline procedures for locating and handling soil and pollen evidence. Understand processes for preserving footwear and tire prints and impressions.

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THREE

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  1. THREE Physical Evidence

  2. LEARNING OBJECTIVES • Distinguish between class and individual characteristics. • Outline procedures for locating and handling soil and pollen evidence. • Understand processes for preserving footwear and tire prints and impressions. • Summarize techniques for collecting glass and paint evidence. • Discuss methods of collecting and storing fibers, cloth fragments, and impressions. • Understand how to locate, identify, and use tools to obtain fingerprints. • Describe the importance of forensic dentistry. • Discuss the identification and analysis of bloodstains. • Identify the determinations that can be made from firearm evidence. • Outline techniques for identifying questioned documents. 3-1

  3. THE CRIME SCENE • Defines the location at which an offense was committed • Search the crime scene for physical evidence • Includes a wider area that contains the lines of approach and, • Flight by the perpetrator • The crime scene includes setting of the crime and its general environs 3-2

  4. CLASS AND INDIVIDUAL CHARACTERISTIC EVIDENCE • Class: a group of objects or persons with characteristic physical evidence common to it • Examples include soil and hair • Individual characteristics can be identified as having originated with a particular person or source • Establishes individuality • Examples include fingerprints and footprints 3-3

  5. LOCATING AND HANDLING SOIL EVIDENCE • Soil evidence is important when the suspect drives/walks on unpaved areas • It is picked up by: • tire treads • shoe bottoms • pants cuffs • It may also be located in: • subject's vehicle • articles in a suspect's trunk 3-4

  6. PRESERVING FOOTWEAR AND TIRE PRINTS AND IMPRESSIONS • Footwear prints and impressions should be photographed: • As part of the general scene • Also photograph with a scale • Dental Stone is used in casting impressions 3-5

  7. FOOTWEAR IMPRESSIONS • Photographs of footwear impressions at a crime scene • In the first photo only the impressions are shown • In a subsequent photo a ruler will be added to show sizes • Later casts will be made of the impressions (Courtesy Tampa, Florida, Police Department) 3-6

  8. COLLECTING GLASS AND PAINT EVIDENCE • Paint may be collected from the suspect's tools or clothing. • Paint can often be collected in dried chips. • Glass is a common form of evidence at burglary scenes. • Before any glass fragments are removed from a glass window it should be photographed. 3-7

  9. COLLECTING AND STORING FIBERS, CLOTH FRAGMENTS, AND IMPRESSIONS • Fibers are of greater value as evidence than are rootless hairs. • Fibers may be located on the body of the victim and/or the suspect. • Cloth fragments may be found at the scene of a violent crime. • Cloth fragments may also be found at the suspect's point of approach or exit. 3-8

  10. THREE BROAD CATEGORIES OF LATENT FINGERPRINTS • Plastic prints • Created when the fingers touch against some material such as putty • Contaminated/visible prints • Formed when the fingers are contaminated with such things as ink or blood and touch a clean surface • Latent/invisible prints • Left on a surface from the small amounts of body oil and perspiration that are normally found on friction ridges 3-9(a)

  11. CONDITIONS AFFECTING THE QUALITY OF LATENT FINGERPRINTS • The surface on which the print is deposited • The nature of the material contaminating the fingerprint • Any physical or occupational defects of the person making the print • How the object on which the prints appear was handled • The amount of the contamination 3-10

  12. METHODS OF DEVELOPING LATENT PRINTS • Traditional powders • Fluorescent Powders • Chemicals • Cyanoacrylate of superglue fuming • Visualization under: • Laser • Alternative light • Ultraviolet illumination 3-11

  13. LOCATING PRINTS • Crime Scene Technician • This technician is using powder to develop latent prints • Technicians often wear protective equipment • Several points can be seen (Courtesy Nassau County, New York, Police Department) 3-12

  14. PORTABLE SUPERGLUE FUMING CHAMBER • is used to process the inside and the outside of the car. • is more efficient for processing larger objects. (Courtesy Sirchie) 3-13

  15. FORENSIC DENTISTRY • Forensic dentistry is a specialty that relates dental evidence to investigation • Analyses of bit marks had played a major role in many cases • Teeth marks may be left in food, pencils or other items left at crime scenes • Bite marks can help eliminate or identify suspects 3-14

  16. DENTAL COMPARISON • Dental records are very useful in helping to identify unknown persons who have been the victim of fowl play or who have been reported simply missing. (Courtesy Dr. Richard R. Souviron, D.D.S., ABFO, Chief Forensic Odontologist, Dade County Medical Examiner Department, Miami, Florida) 3-15

  17. IDENTIFYING AND ANALYZING BLOOD STAINS • If blood at the crime scene is fresh and relatively uncontaminated, identification is not difficult • If the conditions at a crime scene are otherwise it is more difficult to identify • One preliminary field test involves the use of Hemident • Blood analyses is important because of the value of DNA typing 3-16

  18. SOURCES OF DNA EVIDENCE • These are common sources of blood and DNA evidence that investigators need to be aware of in conducting crime scene searches. (Source: “What Every Law Enforcement Office Should Know about DNA Evidence.” National Commission on the Future of DNA Evidence (Washington, D.C.: National Institute of Justice, 1999), pp.3-4.) 3-17

  19. HEMIDENT • The use of Hemident in a presumptive or preliminary field test for blood. (Courtesy Lightning Powder Company, Salem, Oregon) 3-18

  20. DETERMINATION FROM FIREARMS EVIDENCE LAB EXAMINATIONS OF FIREARM EVIDENCE MAY ANSWER THE FOLLOWING QUESTIONS • Was this bullet fired from this weapon? • What else can be learned from the bullet? • What determinations can be made from cartridge cases? • What miscellaneous determinations can be made by examination of firearms evidence? 3-19

  21. BULLET IDENTIFICATION • When a bullet passes through the barrel of a weapon distinctive scratches are caused • These scratches can be compared to bullets fired through firearms in question • Identification is affected by the condition of the gun and of the bullets 3-20

  22. COUNTERFEIT SOCIAL SECURITY CARDS • Social security numbers are an important source of identification in America • Criminals often try to produce social security cards in order to assume new identities • Illegal aliens also often try to obtain fake social security cards (Courtesy Immigration and Naturalization Service, Forensic Documents Laboratory.) 3-21

  23. TECHNIQUES FOR IDENTIFYING QUESTIONED DOCUMENTS • Handwriting and handprinting examinations • There are three types of forgery: • Traced forgery • Simulated forgery • Freehand forgery 3-22(a)

  24. TECHNIQUES FOR IDENTIFYING QUESTIONED DOCUMENTS (cont'd) • Photocopier examination • Paper examination • Age of documents • Burned or charred paper • Altered or obliterated writing • Writing instruments • mechanical-impression instruments • Typewriting 3-22(b)

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