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Dactyloscopy

Dactyloscopy. …the study of fingerprints. Fingerprints are useful because… they’re unique they’re consistent over a person’s lifetime we have a systematic classification scheme Why do we even have these ridge patterns? provide a better grip? (friction ridges)

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Dactyloscopy

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  1. Dactyloscopy …the study of fingerprints

  2. Fingerprints are useful because… • they’re unique • they’re consistent over a person’s lifetime • we have a systematic classification scheme • Why do we even have these ridge patterns? • provide a better grip? (friction ridges) • make perspiration easier on a hairless surface? • improve our sense of touch? • Apes and monkeys also have them on fingers and toes

  3. Friction Ridges Can also be found on your palms, feet, and lips They are NOT genetically controlled…even identical twins have different fingerprints! Sweat pores along ridges release perspiration made up of 99% water. After evaporation, the remaining residue consists of salts, organic compounds, and body oils.

  4. 3 Basic Patterns: Loop; at least one ridge enters and leaves from the same side Radial loop opens to radius bone (thumb side) Ulnar loop opens to ulna bone (pinky side) Contain a core and a delta

  5. 3 Basic Patterns: 2. Whorl; at least two deltas and a core 4 types: a. Plain whorl b. Central pocket c. Double d. Accidental

  6. 3 Basic Patterns: 3. Arch; ridges enter on one side and exit on the other (usually no delta or core) Types; a. Plain b. Tented

  7. Frequency: 60% 20% 10% 5% 4% 1% Ulnar loop Plain whorl Other whorls Radial loop Plain arch Tented arch Plain arch Other whorls Ulnar loop Tented arch Radial loop Plain whorl

  8. Henry Classification System Looking for whorls!!! Pg. 81

  9. Ridge Classification Individualizing prints Individual ridge characteristics are called minutiae. No legal requirements in the US regarding the number of points that must match before deciding that a fingerprint belongs to a certain individual. Criminal courts generally accept 8-12 points of similarity.

  10. Types of Fingerprints Plastic; indented or molded prints made by pressing a finger into a plastic-like material

  11. Visible; from a finger that has touched colored material such as blood, ink, paint, mud, dust, etc.

  12. Latent prints; made by the deposit of perspiration or body oils. These prints are invisible to the naked eye until “developed” by some chemical or physical means.

  13. Visualizing Latent Prints • “Dusting” for prints; • Use fine powder that adheres to body oils and perspiration • Use a powder that contrasts with the surface (ex. Use white powder on a dark surface and black powder on a light surface) • Brush away excess powder that does not adhere to the print • “Lift” the print with clear, sticky tape • Works best on hard, non-absorbent surfaces

  14. Chemical Methods Dusting for prints video Developing prints with superglue video

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