Ch. 5 Notes - Fingerprints (Pg. 2-3)

Types of Arches: Plain and Tented - Has a spike in the center

Types of Loops: Radial and Ulnar

Types of Whorls: Plain, Double, Accidental, Central pocket

1. Minutiae

   1. While looking at the basic fingerprint patterns can quickly help eliminate a suspect, in order to positively match a print found at a crime scene to an individual, more information is needed.

   2. Every individual, including identical twins, has a unique fingerprint resulting from unique ridge patterns called minutiae (called this because the details are so minute or small).

   3. Minutiae are pints where print tidges come together or end; they are considered to be the “uniqueness” of an individual.

   4. FBI has found that no two individuals have more than 8 common minutiae.

   5. so many fingerprint experts use this”twelve-match guideline”. when a fingerprint expert takes the witness stand and says he’s absolutely certain two fingerprints match, he means he’s found about twelve or more matching minutiae.

2. Ridge Count

   1. A ridge count is another characteristic used to distinguish one fingerprint form another. to take a ridge count, an imaginary line is drawn form the center of the core to the edge of the delta and intersecting ridges are counted.

3. Types of Fingerprints

   1. Three types can be found at crime scenes:

      1. Patent fingerprints , or visible prints, are left on a smooth surface when blood, ink, paint, grease, or some other liquid comes in contact with the hands and is then transferred to the surface.

      2. Plastic fingerprints are actual indentations left in some soft material such as clay, putty, or wax.

      3. latent fingerprints are caused by the transfer of oils and other body secretions onto a surface.

         1. Latent fingerprints are not visible to the naked eye but can be made visible by using chemicals.

         2. to dust for fingerprints, dust surface with a fine carbon powder to make a fingerprint more visible. Tape can then be used to lift and pressure the fingerprints.

         3. metal or magnetic powders can also be used to lift fingerprints.

         4. The next page has a chart of chemicals and procedures commonly used to lift latent fingerprints.