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Latents Unit


The Latents Unit of the Louisiana State Police Crime Lab covers a variety of analyses, and accepts cases from agencies state-wide for latent print comparison, fire debris analysis, and impression (shoe/tire) comparison. Analysts receive evidence from outside agencies throughout the state, in addition to evidence recovered from cases processed by the Crime Lab.

Analysts in the print comparison discipline receive prints recovered from crime scenes. Direct comparison is made between the unidentified print and reference prints from victims, suspects, officers, or other individuals who may have touched the evidence on which prints were developed. Unidentified prints are routinely searched through the state and federal fingerprint databases, AFIS (Automated Fingerprint Identification System) and NGI (Next Generation Identification). These databases house known finger and palm prints from arrestees, applicants (nurses, concealed carry permits, etc.), law enforcement, and military, as well as unidentified prints.

Fire Debris analysts can furnish fire scene investigators with information relating to the presence and classification of an ignitable liquid at a fire scene. Fire debris analysis cannot determine whether a fire was intentionally set, and cannot identify a specific source of the ignitable liquid residue. The presence and classification of an ignitable liquid, which may be used to start or accelerate the spread of a fire, is determined by analysts using a gas chromatograph/mass spectrometer (GC/MS).

Impression comparisons are typically conducted between a questioned impression and known shoe or tire impression. Wherever a crime has been committed, someone has had to enter and exit the scene. In the process, shoeprints, footprints, and tire tracks can be left. These types of impressions are encountered on a wide variety of surfaces and different collection techniques may be utilized. Proper processing of each surface type may result in collection of impressions which can, in some cases, be positively matched to a specific shoe or tire.

Analysts provide expert witness testimony across the state and routinely provide free training and assistance to Law Enforcement Agencies throughout Louisiana. All analysts in the Latents Unit are members of their respective state, national, and international professional organizations and maintain a presence in these organizations through OSAC working groups, technical committees, and research. All Latent Print Examiners in the unit are certified as CLPE's through the International Association for Identification (IAI), and our Impression Comparison Analyst is certified as a CFWE through the IAI.


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