Fingerprints, palm prints, and foot prints are impressions of the friction ridge skin present on the palm side of the hand and soles of the feet. When a person touches, grabs, or walks barefoot on a surface an impression of the friction ridge skin may be left behind. These unintentional impressions are called latent prints.
The importance of latent print evidence is its ability to identify an individual. Latent prints can be identified to a single person because the friction ridge skin possesses two key properties: permanence and uniqueness. With the exception of injury, a person has the same fingerprints, palm prints, and foot prints from sixteen weeks gestation until decomposition after death. Additionally, the friction ridge skin has unique characteristics which allow even a small portion of a latent print to be identified to a single person.
Latent prints left on a surface can be visualized through a variety of chemical and physical development techniques. Once visible, the latent print can be photographed and compared to the known inked fingerprints (or palm prints or foot prints) of an individual. Through careful analysis and comparison of the friction ridge skin characteristics in both the unknown latent print and the known inked print, a person can be identified, or eliminated, as having made the print.
Latent fingerprints may be searched through the Automated Fingerprint Identification System (AFIS). AFIS is a computer-based system which compares fingerprints entered into the system with those already in the system.