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Fingerprinting

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A criminal left fingerprints at a crime scene. Now, it’s up to you to identify the person’s fingerprints from a database of suspects. You’ll use the Henry Classification System to break fingerprints down into simple features to best categorize them. And along the way you’ll find out how a whorl differs from a loop or an arch. A keen eye, some simple mathematics, and exacting detective work are needed to solve this crime. Now it’s up to you to find out “who done it?”

Fingerprinting Brochure

Fingerprinting Brochure

What is a human fingerprint?

A human fingerprint is an impression made by the epidermal or friction ridges on the inside end of the finger. These friction ridges are useful when picking up objects with the fingers. The ridges also help increase sensitivity felt by a person when the fingers are moved across a surface. Fingerprints are one of the most useful biometric identifiers of a person. The fingerprint impression is made when ink is placed on the tips of the fingers, then pressed against a material with a light background. The print shows the pattern of the ridges on the tip of the finger.

Are all human fingerprints unique?

The answer is a resounding, "maybe." So far, no two human fingerprints have been found to be identical. That does not mean that it is not possible, only that the probability of two individuals having identical prints is very, very low. Every human on Earth would have to be printed and compared to accurately make the "all fingerprints are unique" statement. And this is very unlikely to occur.

What are the major types of human fingerprints?

Based on the patterns displayed, human fingerprints can be classified into three major groups. These groups are arches, whorls, and loops. The figure below shows each type of print.
Supplemental Background Figure

What is the Henry Classification System?

The Henry Classification System (HCS) uses prints from all ten fingers from a person to group prints by major patterns. This method reduces the time and eyestrain needed to identify a single fingerprint based on the print's gross anatomical features. In the HCS, each finger is assigned a value. The left pinky is assigned a 10, and the value reduces by one moving inward from the left pinky. The left thumb, therefore, has a value of 6. The right thumb starts with a value of 1 and increases as it moves outward to the right pinky, which has a value of 5. The arch and loop fingerprint types are ignored in this system. Each whorl fingerprint type is assigned a value as shown in the table below. Once a set of prints have been assigned values using the table, the following equation is used to determine the primary grouping of the print. The HCS system allows 1,024 primary groupings of fingerprints. Primary grouping ratio =
(1 + (sum of whorled, EVEN finger value))(1 + (sum of whorled, ODD finger value))
Supplemental Background Figure

What are some other ways human fingerprints are categorized?

Most modern fingerprinting systems, such as the Integrated Automated Fingerprint Identification System, have discarded the HCS and now rely on ridge counting and other print characteristics. In fact, most fingerprint identification systems have now become what is termed a "lights outs" identification process since no human is involved in the process; the entire identification is now completed by a computer.
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