What’s in a Print? What Police Officers Need to Know About Latent Prints

January 19, 2023    |    4 minute read

What’s in a Print? What Police Officers Need to Know About Latent Prints

January 19, 2023    |    4 minute read

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Fingerprints have been the standard for personal identification for more than a hundred years.  Fingerprints are used to ascertain the individuality of a person so that they can be identified.  Usually, no crime can be committed without the assistance of one’s hands because they are the prime body part of that person.

Fingerprints help police and investigators in a myriad of ways.  They help to identify a potential suspect, link one crime scene to another involving the same person, track a criminal’s record, track their previous arrests and convictions, aid in sentencing, probation, parole and pardoning decisions.

Where Fingerprints Are Found

Fingerprints can be found on practically any solid surface, including the human body.  Analysts classify fingerprints into three categories based on the type of surface where they are found and whether they are visible or not.  Fingerprints on soft surfaces such as soap, wax or wet paint are likely to be three-dimensional plastic prints.  Visible prints are formed when blood, dirt, ink or paint are transferred from a finger or thumb to a surface.

What Is a Latent Print?

Latent prints are formed when the body’s natural oils and sweat on the skin are deposited onto another surface.  Latent prints can be found on a variety of surfaces, however, they are not readily visible and detection often requires the use of fingerprint powders, chemical agents or alternate light sources.  The smoother and less porous a surface is, the greater the potential that any latent prints present can be found and developed.

How Latent Prints Are Collected

One of the most common methods of discovering and collecting latent fingerprints is by dusting a smooth or nonporous surface with fingerprint powder.  If any prints appear, they are photographed and then lifted from the surface with clear adhesive tape.  The lifting tape is then placed on a latent lift card to preserve the print.

Generally, the smoother and less porous a material is, the higher the probability that the forensic investigator will be successful in developing any latent prints for evidentiary purposes. Items such as glass, polished woods, plastics, and some metals do not permit the oils and excretions deposited from an individual who touched these items, to soak in. This allows for the latent print to be processed and collected easier than if the item was porous. However, with the use of chemicals and different light sources, latent print can be recovered from surfaces such as cardboard, paper products and unfinished wood. These porous surfaces do allow for the individual who touched the items to soak into the material and leave a permanent mark. If the correct chemical and development method is used, positive results can be obtained for latent evidence.

Once latent print is processed, the forensic investigator will determine if any are identifiable. If the print is deemed identifiable, the forensic investigator can determine the identification of an individual who the unknown latent print belongs to by entering that print into an Automated Fingerprint Identification System (AFIS), such as AFIX Tracker.

What Are Latent Palm Prints?

For years, fingerprints were the only prints relied on to identify a perpetrator of a crime.  Now, with advancements in biometric technology, palm prints can also be used for identification purposes.   It is estimated that 30 percent of latent prints found at crime scenes come from palms.  Latent palm prints can be much more helpful to investigators than latent fingerprints, for the sheer fact that there is more surface area in palm prints—fingerprints have 150 characteristics, while palm prints have 1,500.  But as is the case with fingerprint evidence, the quality of the palm prints are very important.

Fingerprint identification has been associated with law enforcement and forensic applications for more than 100 years.  And now, with the assistance of biometric technology, latent fingerprint and palm print identification remains the most prominent method in crime scene investigations.  Searching and collecting latent prints are the activities done by forensic experts whenever a crime takes place.  With the help of an AFIS system, like AFIX Tracker, latent prints can be identified and then further analyzed by an expert in forensics and then used to convict a criminal at trial.

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