Classifying Fingerprints

Fingerprints were one of the earliest methods  used for identification of people who had committed a serious crime. In the 1890′s Sir Edward Henry spent many years describing fingerprints from many people and discovered there are 4 main ways of classifying fingerprint patterns – arch, loop, whorl and composite. A historical account of how fingerprinting was developed provides useful background information. An expert uses guides to make sure their analysis of the evidence is accurate.

The reasons why fingerprinting techniques became so useful in identification is because no two individuals can have the same fingerprint patterns. Even in the case of identical twins, when two individuals have exactly the same DNA, their fingerprints are different. This is because even though the patterns of ridges have some genetic basis, they are also affected by environmental conditions as they develop in the embryo. Once the pattern has formed it becomes a permanent pattern and remains the same apart from damage due to scarring throughout a person’s life.

The other key reason that fingerprint techniques developed is the fact that the human skin is constantly secreting oils onto the surface in order to maintain the skin’s subtle and flexible nature. These oils, though transparent, are left behind whenever a person touches a surface. The prints that are left behind are called latent fingerprints. They are not generally visible to the naked eye unless left on a surface like glass. However, by dusting an area of a crime scene with white or black powder, the prints are much more easily seen. Furthermore, when a person is nervous, they are more prone to sweating and secreting more oils than usual, exactly the sort of conditions which are likely to occur during a crime. This increases the chance of detectives being able to obtain prints of the perpetrator.

To learn how to classify fingerprint patterns go here.

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