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Fingerprints

Fingerprints. Background Information. Each fingerprint is made up of friction ridges, that do not change over time (unless scarring occurs) Fingerprints are formed in the womb Each fingerprint is a deposit of wastes when a person comes in contact with a surface

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Fingerprints

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  1. Fingerprints

  2. Background Information • Each fingerprint is made up of friction ridges, that do not change over time (unless scarring occurs) • Fingerprints are formed in the womb • Each fingerprint is a deposit of wastes when a person comes in contact with a surface • 98 % is water & salts, 1% oils, 1% amino acids

  3. Prints at a Crime Scene • Divided into 3 types • Patent Print • Plastic Print • Latent Print

  4. Patent Print • Can be seen with the naked eye • Made by a hand that had blood, grease, oil, or any other sticky substance on it

  5. Plastic Print • Visible to the naked eye • Formed when an impression is made in a soft substance such as putty, glue, dust, or butter

  6. Latent Print • Most common type • Cannot be seen without applying powder or chemicals • Substances adhere to the amino acids or oils in the fingerprint and make it visible

  7. Patterns of Fingerprints • 3 basic types of patterns • Arch : 5% of population • Loop : 65% of population • Whorl : 30% of population

  8. Basic Fingerprints

  9. The Arch • Formed when the ridge lines go from one side, rises in the middle, and leaves on the other side (like a wave) • Tented arches are more pointed • No ridgecount

  10. Example of Arch

  11. The Loop • Ridge lines enters & exits on the same side of the finger • Type is determined by the direction the ridges come & leaves • If it is from the thumb-side of the finger, it is called a RADIAL LOOP • If it is from the little finger side it is called an ULNAR LOOP

  12. Examples of Loops

  13. The Delta • Whorls are subdivided using a ridge characteristic called a DELTA • DELTA: Triangle pattern (ridge forks & nearby ridge) • Whorls have 2 deltas, loops have 1 delta & arches have 0 deltas

  14. The Whorl

  15. Ridge Characteristics • BIFURCATION (or fork): ridge splits into 2 friction ridges • ENCLOSURE: forms an oval • ENDING RIDGES: ridges that stop abruptly

  16. Ridge Characteristics Continued • SHORT RIDGES: begin & end abruptly, traveling a short distance • RIDGE DOT: isolated ridge that’s length is approximately its width

  17. Examples of Ridge Characteristics

  18. Identifying Fingerprints • 8-12 points of comparison must be in common to declare the 2 prints a match • When a partial print is available, as many characteristics must be matched as possible • Characteristics can be matched to the AFIS (Automated Fingerprint Identification System)

  19. Example of Positive ID

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