Many very good articles and books have been written on fingerprint technology. For the crime scene investigator or evidence recovery technician assigned the task of recovering fingerprint impressions at the crime scene, it is important that they have a good solid foundation of the basic knowledge. The knowledge should include the basic terminology, the equipment that is available , safety standards for the products being used and the basic skills that are being applied in the field.

Fingerprint identification
In criminal investigations fingerprints are one of the oldest and most common types of physical evidence found at a crime scene. One of the primary goals of the investigation deals with identification. Whether the identification is that of an unknown victim (body found at the side of the road) or that of the perpetrator of a crime. The ridge detail developed and recovered at a crime scene and later identified by a fingerprint examiner becomes an investigative lead (starting point) for the detectives assigned to the investigation. A fingerprint is simply defined as friction ridge detail of the hands and the feet. The friction ridges serve two basic purposes. First they allow us to grip and hold on to various surfaces. In forensics, they serve as a method of individual identification.

Fingerprints and The Crime Scene Investigator/Technician
Departments and agencies throughout the country vary as to whom is assigned the duties of processing the crime scene and recovery of the latent impressions.

The goal of the crime scene investigator or evidence recovery technician is recognition and recovery of friction ridge detail that might be deposited on the many different surfaces at a crime scene. The crime scene investigator/technician must have an understanding of the types of ridge detail that may be deposited on the scene, the types of surfaces that would retain the detail, and the methods used in recovering those deposits. The biggest challenge for technology today is adopting to keep up with the ever-changing surface materials.

Categories of prints
Different regions of the country have different phrases used to describe the terminology and techniques in ridge detail deposit and recovery. There are three basic categories or types of impressions that may be deposited, detected, developed if need be and recovered at a crime scene.

1. Latent
The skin has deposits of oil and perspiration that normally coat the surface. When the hand touches the surface, some of the moisture is transferred from the hand to the object, leaving an impression of the friction ridge detail. These are referred to as latent impressions. On most surfaces the latent impressions are not readily visible. The word latent is defined as not visible. That does not mean that it is actually invisible. Using available or oblique lighting on most surfaces will reveal the impression. The impression must be enhanced or developed to be seen fully and collected.

2. Patent
A patent impression occurs as the result of transferring a foreign material coating the skin of the fingers. Examples of the foreign material would be substances like paint, tar, grease, blood, or ink. The best example of a patent impression would be the ink standards or elimination's that we as investigators collect from individuals. After the ink is applied it becomes the foreign material coating the hands of the individual. A card is used as a transfer medium, thus becoming the object touched and a transferring of the patent impression takes place. The word patent means obvious or evident. Patent impressions are visible and usually need no enhancement. They are simply photographed and the item that they are deposited on is collected if necessary. The photograph and or object actually becomes the investigators lift.

3. Plastic or Molded
A plastic or molded impression is deposited when the hands, fingers, or feet is pressed into a soft rubbery type material that will retain the impression of the ridge detail. Where a latent impression is deposited on the surface, a plastic or molded impression would be deposited into the surface. Examples of the materials where a plastic impression would be deposited are clay, wet paint , blood, or tar. Plastic or molded impressions are visible and usually need no enhancement. They are simply photographed and if necessary the item is collected and may have the ability to be caste.

As a further example; If we were to ask the question, "Is a bloody print the same as a print in blood" ? The answer to this question would be, "NO". The print in blood would be an example of depositing a plastic or molded impression into the surface of blood. The bloody print would be an example of having a foreign substance, such as the blood, coating the hand and depositing an impression from the blood coating to another surface.

Discovery
The discovery process or visual search for a latent impression starts at a point of entry and works the way into and surrounding the crime scene. The search is to discover items that have been handled, moved or anything that appears out of place. The most suitable surfaces are smooth, hard, non-absorbent and non-porous surfaces. Patience, common sense, and experience are needed to assure that all latent impressions are collected. Continued practice will give the confidence needed to collect all types of impressions from different surfaces.

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