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Fingerprints

Fingerprints. Reasons they became useful. Discovered that they are unique. No 2 alike. A classification system was developed. Loops Whorls Arches. Classification. Computer database AFIS Automated Fingerprint Identification System 1990

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Fingerprints

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  1. Fingerprints

  2. Reasons they became useful • Discovered that they are unique. No 2 alike. • A classification system was developed. • Loops • Whorls • Arches

  3. Classification • Computer database • AFIS Automated Fingerprint Identification System • 1990 • IAFIS Integrated Automated Fingerprint Identification System • Criminal histories; mug shots; scars and tattoo photos; physical characteristics like height, weight, and hair and eye color; and aliases. • Response time: • 10 minutes for electronically submitted criminal prints. • One hour for electronically submitted civil prints.

  4. Patterns • Loop – comes in one side and out that same side. One delta on the side opposite from where it starts and exits. Most common Turn Enter Delta Exit

  5. Patterns • Whorl – Circular shape. Two deltas on either side. Delta Delta

  6. Patterns • Arch – Up thrust, with a decline. Exits opposite side. Up Thrust Enter Exit

  7. Types of fingerprints at crime scene • Plastic – finger contacts a soft surface such as putty. • Visible. Finger is covered with a liquid such as blood and then contacts a hard surface. • Latent – Invisible. Oils, salts and other debris stick to a surface when it is touched by a finger. Most common.

  8. Methods to search for fingerprints • Lighting – flash light, etc. • Chemical reaction • Iodine mixes with starches in the fingerprint and turns brown • Ninhydrin mixes with the amino acids in the fingerprints and turns purple.

  9. Methods to enhance a fingerprint • Dusting with fingerprint powder • Gray – aluminum dust • Black – carbon or charcoal • Ultraviolet image converter – Reflected Ultraviolet Imaging System (RUVIS) • Iodine Fuming • Not permanent • Must be photographed

  10. Methods to enhance a fingerprintCont. • Ninhydrin • Amino acids • Turns purple within an hour or two. • Physical developer • Silver nitrate based liquid reagent • Good for porous surfaces

  11. Combination methods • Used for slick surfaces. • Superglue and dusting.

  12. Steps in identifying a fingerprint • Identifying the pattern (loop, whorl, arch) • Looking for minutiae • Ridge ending • Bifurcation • Island • Core • Delta • Cicatrix

  13. Questions • What do you compare a lifted print to? • A known sample • How many points does the FBI use in identifying a print? • 14 • How does a fingerprint match become confirmed? • With a microscopic match by a human being.

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