Fingerprint notes

Delta: a triangular ridge pattern with ridges that go in different directions above and below a triangle


Arch: Fingerprint pattern where ridge starts on one side and finishes on the other, 5%, no deltas


Loop: Fingerprint pattern where the ridge starts on one side, loops around, and finishes on the same side, 65%, one delta

   Types: Radial Loops (start on thumb side) and Ulnar Loops (start on pinkie side)


Whorl: Fingerprint pattern where ridges form a bullseye, 30%, two deltas

    Types: Plain whorl (deltas transect the whorl)

Central Pocket Loop (deltas don’t transect)

Double Loop (ying-yang)

Accidental Loop (irregular shape)


Core: center of a loop or whorl


Minutiae: combination of unique details in the shape and position of the ridges that make each fingerprint unique


Ten Card: form used to record a person’s fingerprints


IAFIS/AFIS: Integrated Automated Fingerprint Identification System, a database of fingerprints created by the FBI, operates 24 hours a day, 365 days a year.  Allows for identification of fingerprints within two hours, contains more than 47,000,000 people


Fingerprint: raised ridges of skin on your fingers and toes called friction ridges.    No two fingers have been found to have the same identical ridge characteristics

  Function: increases sensitivity to touch

  Water, oils, salts, and dirt are left behind when you touch something

  Chinese used fingerprints to sign legal documents over 3000 years ago.

  A fingerprint remains unchanged during an individual’s lifetime.  It is impossible to eliminate 

       all the minutiae

  If an injury reach 1-2 mm into the skin it will form a new permanent minutiae in the form of a 

    scar

  Each ridge has a series of pores from which sweat (water) and oils come from


Types of Fingerprints

  1. Patent – visible fingerprints left on a smooth surface when blood, ink, or some other liquid comes into contact with the hands and is transferred to the surface

  2. Latent – invisible fingerprints created by the transfer of oils or other body secretions

  3. Plastic – actual indentations in a soft material such as clay, mud, wax, putty






Fingerprint formation

  1. Pattern starts to form at 10 weeks of pregnancy and complete when the fetus is 6 months old

  2. The basal layer grows faster than the rest of your skin, causing it to fold in on itself creating ridges (dermal papillae).  This creates the pattern of ridges



Ridge Patterns

  1. Whorls – 30%, has two deltas

  2. Loops – 65%, has one delta

  3. Arches – 5%, has no deltas


Minutiae (Specific ridge characteristics)

  Average print has 150 individual minutiae

  To be a match, the two prints in question must have 8-12 minutiae in common along with the 

     same ridge pattern


Fingerprint Comparison

Level 1: Identification of general ridge patterns (whorl, loop, arch)

Level 2: Identification of minutiae

Level 3: examine and locate ridge pores, breaks, creases, scars and other permanent minutiae


Evaluation

  1. Identification: latent print and suspect come from the same source: POSITIVE MATCH

  2. Exclusion: Latent print and suspect did not come from the same source: NO MATCH

  3. Inconclusive: Cannot determine if the latent print and suspect come from the same source with a strong sense of certainty.