Analyzing Fingerprints

What causes fingerprints? Fingerprints are caused by the ridges (raised parts) and valleys (non-raised parts) on the end of the finger. Oils and sweat in the configuration of these ridges are left behind when you touch things. Your unique configuration of these ridges and valleys create your fingerprint pattern.

3 General Fingerprint Patterns The 3 general patterns are: Whorl Loop Arch

Whorls Whorls are swirly patterns consisting of a series of irregular circles or spirals around a central core. There is no identifiable end to the ridges.

Loops Loops look like opened whorls --- parts of concentric circles are somewhat squashed and surround a core. The core of a loop is the bend of the innermost ridge of the loop. The ridges enter from one side, curve around the core, and exit on the same side they entered.

Arches This is the least common type of print It is especially uncommon to have arches on your “pinky” finger. Arches do not curve back upon themselves at all. They enter from one side of the print and exit on the other. Arch have no core.

5 Basic Characteristics These characteristics are called Galton Characteristics after Sir Francis Galton. They include the fork, dot, ending ridge, enclosure, and short ridge.

Characteristics Galton noted in his book “Finger Prints”

Fork (Bifurcation) Notice the ridge pattern characteristics on each print.

Dot Each of these characteristics is unique to each print.

Ending Ridge Fingerprints are compared in the AFIS system AFIS is the automated fingerprint identification system

Enclosure (lake) AFIS compares all of the characteristics of fingerprints to find a match

Short Ridge Your fingerprints may be in the AFIS system because: You committed a crime in the past You were fingerprinted for school or work You were fingerprinted (often as a child) for identification purposes

Trifurcations Point at which one friction ridge divides into three friction ridges 

Spurs (Hooks) bifurcation with one short ridge branching off a longer ridge

Bridges A connecting friction ridge between parallel running ridges, generally right angles

Ridge Crossing Point where two ridge units intersect

Two Identification Points The focal points used for identification include the delta and the core.

The delta consists of a fork and a nearby ridge or dot. All whorls have 2 or more deltas, loops have one and arches have no delta.

Are there variations between the types of prints?

How is the use of fingerprints for identification better than the old system of Bertillon measurements?