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CSI'/ Forensics Fingerprint Identification
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CSI'/ Forensics Fingerprint Identification

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  • 1. Forensics
    Identification of Fingerprints
  • 2. Fingerprints
    No 2 people have the same fingerprints
    Fingerprints can solve crimes.
    Fingerprints are impressions created by ridges on the skin.
    Ridges form before a baby is born and maintain their pattern throughout life.
    As you grow, the pattern gets larger, but does not change.
  • 3. 2 layers of skin
    Dermis, the deepest layer which contains sweat glands, oil glands, nerves, and blood bessels.
    Epidermis, made of several layers of cells that are arranged along ridge patterns.
    Outter-most cells of the epidermis are dead and they dry out and fall off.
  • 4. Latent Prints
    When a person touches an object, the perspiration, oils, and amino acids on his or her skin are transferred to that object. Sometimes an impression of the ridge pattern is left in the deposit.
    Fingerprint—the impression left
    Prints are not usually visible to the naked eye, so they are called latent (hidden) prints.
  • 5. Classification of fingerprints
    Fingerprints have general patterns of ridges that allow them to be classified and compared. All fingerprints are divided into three large groups, based on their ridge pattern.
  • 6. Loop
    Loops are found in 65% of the population
  • 7. Whirl
    Whorls are found in 35% of the population
  • 8. Arch
    Arches are found in 5% of the population
  • 9. Which is it?
  • 10. Which is it?
  • 11. Basic and composite ridge characteristics
    ridge ending bridge
    Bifurcation double bifurcation
    dot trifurcation
    island (short ridge) opposed bifurcations
    lake (enclosure) ridge crossing
    hook (spur) opposed bifurcation/ridge ending
  • 12.
  • 13.
  • 14. Mini Lab #1: Identifying our Fingerprints
    Pass out worksheet
  • 15. Identify your prints
    Classification and Ridge characteristics
  • 16. Identify LATENT prints
    Latent prints (hidden) must be located and preserved. There are two basic techniques for finding fingerprints.
    1. Dusting
    2. Chemically fixing
  • 17. Fingerprint Dusting
    Hard surfaces such as glass and tile yield prints when lightly dusted with powder.
    Fingerprint powders come in a variety of colors so that the investigator can always apply one that will contrast with the surface holding the print. The powders can be brushed in place with either a camel-hair or fiberglass brush.
  • 18. Chemical fixing
    Chemicals can be used to help find fingerprints on many types of smooth surfaces.
    Forensic specialists may use chemicals to reveal prints and then take pictures of them
    Super Glue fuming produces good prints on nonporous surfaces such as a metal, leather, and plastic. In this technique, Super Glue is heated in an enclosed area that contains the evidence in question. Prints appear in an off white shade.
  • 19. CSI Fingerprint Lab, Part II
  • 20. Pointing out Perpetrators Lab
    When Mrs. Henley walked into her science class, she was surprised by a birthday cake topped with an incredible number of candles. Students broke into an off key rendition of “Happy Birthday” and gave her a standing ovation.
    “For the first time, I’m speechless”, Mrs. Henley said. “I can’t believe you guys prepared this birthday surprise for me. Do you really think I need all these candles? Before we eat, tell me who brought the cake, dishes, forks, napkins, and drinks? I want to thank you personally.”
  • 21. No one spoke as Mrs. Henley looked around the room, waiting for a response. “What’s the matter? Are you bashful? Who brought all of this good stuff?”
    Still the students smiled and remained silent. Mrs. Henley was amused, and decided to make the best of the situation. “OK. Lets try something. The birthday party conspirators moved some glass slides from the table to set up the cake. I think we can use these slides to identify our modest hosts.”
  • 22. Super Glue Fuming
    Aquarium with light bulb and super glue set up.
    Fingerprint ID on all students/ worksheet using graphite.
    ID conspirators prints along with whether they have a loop, whorl or arch.
    Determine the % of loops, whorls, and arches in the class for the Data Table.

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