Fingerprints in Forensics--General Types of Fingerprints

In the world of crime scene investigation, there are three kinds of fingerprints that show up at a crime scene. In this article, I will attempt to explain what the three kinds of fingerprints are.

In general, fingerprints come in three types that rely on how and where they were left behind. A fingerprint found on an oily wall is much easier to find than one left on a plastic Wal Mart bag without any visible substance.

The three kinds of fingerprints are as follows:

• Patent fingerprints happen when a medium such as grease, dirt, blood, ink, or paint on the fingers of the offender of a crime leaves behind a readily available fingerprint that is visible to the naked eye.


• Plastic fingerprints have a three-dimensional characteristic and happen when the offender consciously or unconsciously presses a fingerprint into a soft medium such as margarine, soap, caulk, wax, silly putty, or even dust.


• Latent fingerprints are not visible to the naked eye and can not be seen without special light circumstances or special means of processing.

The first two types of fingerprints, patent and plastic, can be photographed. The photograph can be used for comparison. Many times the fingerprint is lighted at a slight angle to increase contrast. However, very little else is required to make these prints capable of being documented. If the offender does not leave behind any visible fingerprints, identification is still likely but definitely more difficult to obtain. The tools for tracking down fingerprints can be as simple as a penlight or black powder as sophisticated as chemical reactions, Super Glue, or lasers. Whichever technique criminal investigators use is dependent upon the surface on which the fingerprint rests. For harder surfaces, powders, in general, are used, and chemicals are many times needed on more porous surfaces. Some fingerprints are visible under an ultraviolet light source or even a small flashlight.

The next time you watch your favorite CSI program, you will have an insight on the terms patent, plastic, and latent fingerprints.

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