Fingerprint Analysis
Fingerprint analysis has been used for identification purposes for over a century and has been a key component to law enforcement for many years. Since everyone has a unique fingerprint, and fingerprints are remain on surfaces because of the natural secretions of the body, fingerprints can be used to confirm identity and prove if a certain person came in contact with an object. DNA fingerprinting has replaced traditional fingerprinting as a more reliable method for some applications, but fingerprint analysis is still a vital part of many different kinds of investigations.
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Basics
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Humans develop what are known as "friction ridges" on their hands and feet. These patterns of raised lines helped us grab and hold onto objects, but they can also be used as identifying features. Every person has a different pattern of ridges. Sometimes the differences are extreme, and sometimes they are slight and require careful observation to notice, but with clear fingerprints it is possible to compare and match samples, showing which person left a particular fingerprint. The ridge patterns develop in the womb and do not change throughout the course of a person's life. This made them key in legal identification for many years, until they were replaced with DNA fingerprinting.
Minutiae
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Fingerprint
The different types of patterns friction ridges take are known as minutiae. Minutiae are divided into several primary categories, such as dots, spurs, lakes and crossovers--small twists and turns that the ridges take as they make the overall shape of the fingerprint. While everyone has these tiny characteristics, the way in which they are occur differs from person to person, making them ideal points to examine.
Leaving Fingerprints
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Finger ridges also have small pores, like the rest of the skin. These pores help the skin to breathe and secrete a small amount of moisture as perspiration, keeping the skin supple and protected. This moisture mixes with natural oils and forms a layer across the finger. When the finger touches an object, these oil is left behind in the shape of an imprint, showing the ridges it came from. Even if a finger is pressed very hard, the way the oil left behind is marked shows where the ridges lie.
Testing
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For a fingerprint to be tested, it must be place on a readable and scannable surface. This is easy when fingers are handy to make imprints from, but when the fingers themselves are absent, fingerprints can be lifted from other objects. The prints last longest on hard, impermeable objects such as steel and glass, where the oil lingers. Fingerprints may be invisible on wood or paper, since the oil is absorb beneath the surface, but advanced scientific techniques can be used to read even these prints.
Legal Cases
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Fingerprinting is used to both establish identity and to confirm the presence of someone in a particular location. To do this, lab technicians must have something to compare the fingerprint sample to. For this reason, there are several large databases of fingerprints that have been collected from people such as convicts and military personnel. Sophisticated software compares certain points from the sample with the fingerprints in the database and finds possible matches.
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