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Fingerprints

Fingerprints. History. 3000 years ago… Chinese used fingerprints for legal papers 1880 Henry Fauld –first to use FP to ID criminals 1897 Sir Edward Richard Henry- -developed Henry classification - based on all 10 prints - number/location of whorls. Skin.

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Fingerprints

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  1. Fingerprints

  2. History • 3000 years ago… Chinese used fingerprints for legal papers • 1880 Henry Fauld –first to use FP to ID criminals • 1897 Sir Edward Richard Henry- -developed Henry classification - based on all 10 prints - number/location of whorls

  3. Skin • Epidermis- outer layer, no blood supply • Dermis-internal layer- sweat glands that produce water, salts, oils • Papillae- at boundary of dermis and epidermis Prints- made of mostly water, salts, oil

  4. Cross Section of Skin

  5. AFIS Automated Fingerprint Identification System

  6. Matching points Also known as: - Minutiae - Galton points Based on types of ridges Match ridges from a known print with an unknown print.

  7. Types of Ridges • Ending ridge • Bifurcation (fork) • Enclosure • Short ridge • Dot • Eye (island) • Bridge • Double bifurcation • Trifurcation

  8. Fingerprints • Friction ridges help human grip things • Identical twins have different fingerprints. • Fingerprints do not change over your lifetime. • Scarring, etc can be used for ID

  9. Deltas • Delta- ridge that diverges • Loops have one delta • Whorls have 2 deltas • Arches do not have deltas.

  10. Types of Fingerprints • 1. Arch • 2. Whorls • 3. Loops

  11. Arches Arches (no core or delta) • Plain • Tented

  12. Whorls • One or more ridges make complete circles • Two deltas and at least one core

  13. Loops • Radial- loop opens to thumb • Ulnar - loop opens to pinky side

  14. Pores • Found randomly along the ridges • Produce sweat • Chemicals in sweat make the fingerprint that is left behind • Pore location can be used to identify the person.

  15. Process of Identification Get prints of all ten fingers from a person in question (suspect, victims, police, etc..) Ways to get the 10 prints • Traditional ink and paper • Roll colorless chemical on treated paper… chemicals react and the print becomes visible (newer) • Live scan: roll prints on glass over video camera. Image is turned into digital information (newer)

  16. Quality of prints • Quality affected by: • Skill and experience of person taking the print • Cooperation of person giving the print • Damaged skin on people who work w/ their hands • Rigor mortis • Decomposition, burned bodies

  17. Types of Prints • 1. Visible (patent) • Bloody prints • 2. Plastic • Tacky paint • Putty • Clay • Soap • 3. Latent • Invisible • Deposit sweat and oil

  18. Methods to Develop Prints • Black powder • Magnetic powder • Iodine fuming (good on paper) • Silver nitrate • Ninhydrin ( for prints on paper) • Super glue (=cyanoacrylate) • Stickyside ™powder

  19. Locating prints • Shine flashlight at oblique angle • Gloves may leave impression • Less obvious places: under toilet seats, toilet handles, tabletops, dresser drawers, surface of dinner plates, back of rearview mirrors, trunk lids of cars • Use someone familiar w/ scene to tell if anything is different about the area

  20. Equipment • Ultraviolet light (black light) Some substances will glow when exposed to UV Ex. LSD– bluish-white Ex. Certain fingerprinting powders glow under UV • Laser • Alternate light source • powerful light causes some materials to fluoresce or luminesce

  21. Daubert Hearings • Fingerprint experts need to convince a judge that the methods used are valid. • Daubert standards: • Has the expert’s scientific method been tested? • Has the expert’s method been the subject of peer review and testing • What is the actual or potential rate of error? • do other scientists generally accept the expert’s methods?

  22. Odds and Ends • If AFIS is used to locate a match, the final identification must be done by a human • Palm prints can also be used • Latent prints can often be developed years later as long as they don’t become wet • Fingerprints made from soot, insulation, face powder are easily destroyed • Prints made from blood, ink, oil can last longer

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