LATENT PRINT DEVELOPMENT

Detecting and developing latent fingerprints from a crime scene are critical functions in a criminal investigation. Latent print development is performed in every kind of case-from a petty theft at a convenience store to murder. It is as much art as it is science. And it is done by field deputies and patrol officers, by criminal investigators and forensic professionals and even by trainees, student interns taking their first step into the world of criminal investigations and forensic science.

Much of the work of developing latent fingerprints is done in the field by Sheriff's deputies or city police officers. They are called to the scene of a burglary or robbery and they search for fingerprints at the site of the crime or on objects at the crime scene. The usual technique is to dust with black powder and then lift the print with tape onto a card. That card becomes part of the evidence in the case and can be compared to the prints of a suspect. When items of evidence are seized and preserved for fingerprinting, the Latent Print Development Section takes over, looking latent prints using a variety of techniques. The lead of the section is a Latent Fingerprint Examiner.

Fingerprint evidence is found on objects that have been touched. Such prints may or may not be visible. Visible prints are those showing ridge detail made by fingers contaminated with substances such as blood, ink, grease or dirt; or are made when fingerprints are pressed into plastic like putty or tar. The majority of fingerprint evidence is not visible, and these prints are called latent prints. Developing the latent print to become visible requires some chemical or physical process.

The ideal surface to obtain fingerprint evidence is a smooth, nonporous object like glass. However, through the use of powders, chemicals, and lasers, fingerprint evidence can be found on a wide variety of surfaces.

Once a print is developed it can be compared to a known suspect or it can be submitted to fingerprint databases for automated searches-to determine if the latent print matches and help solve the crime.