Fingerprints Background Information l Each fingerprint is made

Fingerprints

Background Information l Each fingerprint is made up of friction ridges, that do not change over time (unless scarring occurs) l Fingerprints are formed in the womb l Each fingerprint is a deposit of wastes when a person comes in contact with a surface l 98 % is water & salts, 1% oils, 1% amino acids

Prints at a Crime Scene l. Divided into 3 types l. Patent Print l. Plastic Print l. Latent Print

Patent Print l. Can be seen with the naked eye l. Made by a hand that had blood, grease, oil, or any other sticky substance on it

Plastic Print l. Visible to the naked eye l. Formed when an impression is made in a soft substance such as putty, glue, dust, or butter

Latent Print

Patterns of Fingerprints l 3 basic types of patterns l. Arch : 5% of population l. Loop : 65% of population l. Whorl : 30% of population

Basic Fingerprints ARCH LOOP WHORL Plain Arch Left Radial Loop Left Ulnar Loop Plain Whorl Tented Arch Right Radial Loop Right Ulnar Loop Central Loop Whorl Double Loop Whorl Accidental Whorl

The Arch l. Formed when the ridge lines go from one side, rises in the middle, and leaves on the other side (like a wave) l. Tented arches are more pointed l. No ridgecount

Example of Arch

l Ridge The Loop lines enters & exits on the same side of the finger l Type is determined by the direction the ridges come & leaves l If it is from the thumb-side of the finger, it is called a RADIAL LOOP l If it is from the little finger side it is called an ULNAR LOOP

Examples of Loops

The Delta l. Whorls are subdivided using a ridge characteristic called a DELTA l. DELTA: Triangle pattern (ridge forks & nearby ridge) l. Whorls have 2 deltas, loops have 1 delta & arches have 0 deltas

The Whorl

Ridge Characteristics l. BIFURCATION (or fork): ridge splits into 2 friction ridges l. ENCLOSURE: forms an oval l. ENDING RIDGES: ridges that stop abruptly

Ridge Characteristics Continued l. SHORT RIDGES: begin & end abruptly, traveling a short distance l. RIDGE DOT: isolated ridge that’s length is approximately its width

Examples of Ridge Characteristics

Identifying Fingerprints l 8 -12 points of comparison must be in common to declare the 2 prints a match l When a partial print is available, as many characteristics must be matched as possible l Characteristics can be matched to the AFIS (Automated Fingerprint Identification System)

Example of Positive ID