Forensic scientists and law enforcement officials often rely on fingerprint analysis to identify people who may have been at the scene of a crime or other mystery. They typically analyze and compare sets of fingerprints they find in the field with those in a database of recorded prints. Most analysis is based on the unique patterns of friction ridges on each finger, and there are several ways to uncover fingerprints on surfaces.
Human fingers, palms, toes, and foot soles are typically covered with friction ridges that allow a person to grip objects and the ground. These ridges are also attached to nerves, so the individual may be able to feel even the slightest pressure against the ridge. The ridges create the patterns of fingerprints.
These patterns form on fetuses in the womb and typically remain the same until the body decays after death. They do not change unless there is some form of mutation, injury, or other external change. The fact that fingerprints are, for the most part, unchanging throughout life is one factor that makes fingerprint analysis effective in identifying individuals from their prints.
Another characteristic of friction ridges that aids in fingerprint analysis is the fact that every pattern is different. No two fingers have the same print. Although no study has proven beyond doubt that all fingerprints are unique, in all the years of records, no two have ever been found to be completely identical.
Fingerprints are made up of tiny lines of concentric ridges. There are three general forms these ridges take, loops, whorls, and arches. Many print records are organized into these categories for easier reference during fingerprint analysis.
The ridges also form unique fingerprints based on the tiny variations in their patterns. These small differences are often called minutiae. Common minutiae include ridge endings, ridge splits called bifurcations, spurs that break off a main ridge, and crossovers that connect two ridges. Other minutiae are often called lakes, islands, and dots. Lakes are open places with a single ridge. Islands are short ridges, and dots are tiny ridges that are nearly round.
In fingerprint analysis, there are three main ways that prints are left on objects. First, friction ridges secrete oils and sweat, and when the finger comes in contact with an object, the fluids leave a pattern behind. Second, the secretions may seep into a porous surface, such as paper, leaving a slight stain. Finally, if the finger comes in contact with a liquid or viscous substance, such as ink or blood, the liquid may leave a visible print behind.
These prints are typically photographed if they are visible to the naked eye. Fingerprints that are not easily visible are usually called latent prints. Latent prints must be processed in order to analyze them. Some prints can be made visible to the eye or to scanners through dusting with a fine powder, special lighting, or chemical treatments.