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Fingerprints

Fingerprints. Summary. What are fingerprints? How are fingerprints analyzed? How are fingerprints collected?. Fingerprints. What are fingerprints?. Friction ridge skin pattern. Found on fingers, palms, toes, soles of feet. Composed of ridges (hills) and furrows (valleys). Black = Ridges

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Fingerprints

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  1. Fingerprints

  2. Summary • What are fingerprints? • How are fingerprints analyzed? • How are fingerprints collected?

  3. Fingerprints What are fingerprints? • Friction ridge skin pattern • Found on fingers, palms, toes, soles of feet. • Composed of ridges (hills) and furrows (valleys) Black = Ridges White = Valleys

  4. Fingerprints What are fingerprints? • Develop in early embryonic development. • Pattern based on genetics, detail somewhat random • Identical twins do not have identical fingerprints

  5. Fingerprints How are fingerprints analyzed? Categorized by pattern and minutiae

  6. Fingerprints How are fingerprints analyzed? Patterns Arch Loop Whorl

  7. Fingerprints How are fingerprints analyzed? Minutiae Bifurcation Ridge Ending Dot Island

  8. Fingerprints Computer software compares the location of these minutiae.

  9. Fingerprints History of Fingerprints • Long history of fingerprints as signature • Criminal identification first done by a system of body measurements called anthropometry. • Bertillon’s anthropometry system used 11 body measurements to identify an individual

  10. Fingerprints History of Fingerprints • Henry invented a system for classifying fingerprints. • Allowed fingerprint records to be searched. • Based on all 10 prints, so matching one print would be difficult.

  11. Fingerprints

  12. Fingerprints Modern Fingerprint Analysis • Computer system stores patterns and minutiae of prints • AFIS: automated fingerprint identification system

  13. Fingerprints There are 3 types of fingerprints • Visible – left by dirt, grease, blood, etc. • Does not need processing

  14. Fingerprints There are 3 types of fingerprints • Impression – indentation in soft material (butter, putty, tar, etc.) • Does not need processing

  15. Fingerprints There are 3 types of fingerprints Latent – requires processing to make visible and suitable for analysis

  16. Fingerprints > Analysis What are the invisible components? Multiple sweat glands secrete onto fingers, palms, etc. Sweat contains: • Inorganic ions (Na+, Cl -) • Proteins, amino acids • Lipids • Other

  17. Fingerprints > Analysis Development and Collection: Scene or Lab? • No rule: Depends on situation • Fingerprint must be photographed after development (scene or lab)

  18. Fingerprints > Analysis Physical Development: Dusting • Apply powder to latent print or area. • Powder adheres to print. Brush and Powder

  19. Fingerprints > Analysis Physical Development: Dusting • Apply powder to latent print or area. • Powder adheres to print. Magnetic Brush and Powder

  20. Fingerprints > Analysis Chemical Development: Silver Nitrate • No longer used (messy, not sensitive) • Silver reacts with Cl - ions in print

  21. Fingerprints > Analysis Chemical Development: Iodine Fuming • Iodine sublimes (solid → gas) • Iodine reacts with lipid components; becomes trapped in the print. • Fuming wand or chamber Dirty Brown Color

  22. Fingerprints > Analysis Chemical Development: Ninhydrin • Reacts with amino acids; purple color • Painted or sprayed on area • Heated to react

  23. Fingerprints > Analysis Chemical Development: Super glue fuming • Fumes with heat or base (NaOH) • Fumed in cabinets • Off-white print

  24. Fingerprints > Analysis Chemical Development: Ninhydrin and super glue prints can be further processed: • Dusted • Chemically treated to fluoresce (using laser or alternative light)

  25. Fingerprints > Collection Collection of prints: Tape lift: • Tape placed over developed print • Tape then placed on white card.

  26. Fingerprints > Collection Collection of prints: Sometimes a photograph will be the only permanent record.

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