Criminal Investigations Suspect identification

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Criminal Investigations Suspect identification
2014-05-21 18:00:09
Criminal Investigations Suspect identification
Criminal Investigations
Criminal Investigations Suspect identification
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  1. Fingerprint identification
    Dactyloscopy: the study of fingerprints for ID purposes
  2. Stages of the fingerprint process
    Developing Latent prints:1) photograph the item2) photograph the fingerprint itself
  3. different types of fingerprint patterns. (the frequency that they occur in the population)
    1) loop - ridges enter one side, re-curve and exit. most common, 60%

    2) whorl - ridges encircle a central circular pattern. 35%

    3) arch - ridges enter one side, rise in center and flow out the other side (5%)
  4. admissibility of fingerprints (common origins requirements)
    Latent fingerprints are compared by experts with the suspects.

    since most recovered prints are partial prints, experts compare patterns, and then a point by point comparison.

    no specific number of points must be made, but most courts require 10-15 ridges that are identical in both appearance and location to justify a common orgin
  5. Various methods of latent fingerprint development (chemical and non-chemical)
    • Latent (invisible) Fingerprint: ridge impressions from sweat pores leave oily residues on surfaces.
    • Invisible until something make them visible 

    • For non-porous materials
    • Dusting (most common)
    • spraying
    • alternative light sources
    • superglue fuming
    • small particle reagent

    • Porous material
    • chemical methods - iodine fuming, ninhydrin
    • may produce prints only temporarily, and require immediate photoprahpy
  6. Sound spectrograph
    Sound spectrograph is used to convert the sound of the voice recorded on magnetic tape to the visual form.
  7. voiceprints
    • Voiceprints: also known as spectrograph, is the only legally admissible voice identification system. it compares acoustical patterns for visual similarities
    • no two people have identical vocal chords, nasal cavities, and other body parts responsible for speech
  8. Live-Scan fingerprinting
    Live-Scan fingerprinting: computerized fingerprint processing and identification. process allows police to place a suspect's fingers on a glass plate for recording (no ink)

    Automated fingerprint identification system (AFIS)