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Public Enemy #1

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Look at your fingertips. The unmatched combinations of swirls and lines can physically identify who you are. But it took years of testing to prove that fingerprints were unique.

At the beginning of the 20th century, fingerprinting gained acceptance as a means of identification. Among the first to record their prints were civil servants and soldiers. When it came to identifying criminals, however, people were hesitant to trust that fingerprints were indeed unique. Advocates convinced juries that each print was unmistakably distinct by staging demonstrations using the jurors' own fingerprints.

As identification by fingerprint gained credibility in the courtroom during the 1930s, the number of fingerprint files grew from thousands to millions. New automated technologies improved the organization and sorting of files, enabling investigators to examine prints more efficiently. A new breed of crime fighter could now be found inside a crime lab armed with a magnifying glass and a stack of 8x8 white cards. In 1937 the first case to support a conviction based solely on fingerprint evidence took place in New York. The age of "scientific crime detection" had begun.

There are three main types of fingerprint patterns -- arch, loop and whorl.

Arches can be plain or tented.

The ridges of the plain arch follow a general flow from one side to the other with slight waves in the center.

The more complex tented arch has a defined angle or upthrust at its center.

The loop is the most common pattern occurring in about 65% of fingerprints. Loops must contain three characteristics -- a recurve, delta and a number of ridges between the delta and core.

The ridges flow from one side, recurve and flow back toward the side from which they entered. Loops can be ulnar -- ridges flow toward the ulnar bone (or little finger) or radial -- ridges flow toward the radius bone. The number of ridges that appear between the delta and the core is the ridge count.

The whorl pattern consists of two deltas with a recurve in front of each.

There are four types of whorls.

The plain whorl consists of two deltas, at least one circular ridge and recurving ridges within the pattern area. If you were to draw a line between the two deltas, the recurving ridges would cross or touch that line.

Central Pocket Loops are similar to plain whorls but the recurving ridges would not touch the line drawn between the two deltas.

Double loop patterns are made up of two separate loops and two deltas.

The accidental whorl is a pattern that does not fit into any of the other categories. It usually consists of a combination of two or more patterns.

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