Types of Fingerprints

Over the past sixty years, television has always been a reflection of our society. The programs are an indication of the norms, values and interests that society holds dear at any given time. Crime shows, detective stories and police tales have historically been a staple of the country's television viewing habit, and the country has always had a fascination with these kinds of shows. Today's programs, such as the most popular TV program over the last five years, C.S.I., bring a level of sophistication to the viewing audience that producers of the early crime shows, such as "Peter Gunn" and "Seventy-Seven Sunset Strip," never dreamed was possible. America has always had a fascination with the solving of crimes, and fingerprints are one of the most common types of evidence that investigators search for at crime scenes.

One of the main tasks of the crime scene investigator is to recover fingerprint impressions in order that a positive identification can be ascertained. Since no two individuals have the same fingerprint pattern and these remain unaltered during the course of a person's lifetime, the main type of physical evidence that can be extracted from a crime scene are fingerprints.

There are three distinct types of fingerprint impressions that can be recovered from a crime scene or a scene of interest for investigators looking for some clues as to a missing person, or for other identification purposes. These categories are as follows:

PATENT PRINTS - are visible prints that occur when a foreign substance on the skin of a finger comes in contact with the smooth surface of another object. These prints leave a distinct ridge impression that is visible with the naked eye without technological enhancement of any kind. The tried and true "blood on his hands" evidence is an example of patent prints recovered from a crime scene or scene of interest to investigators. These foreign substances contain dust particles which adhere to the ridges of the fingers and are easily identifiable when left on an object.

PLASTIC PRINTS - are visible, impressed prints that occur when a finger touches a soft, malleable surface resulting in an indentation. Some surfaces that may contain this type of fingerprint are those that are freshly painted or coated, or those that contain wax, gum, blood or any other substance that will soften when hand held and then retain the finger ridge impressions. These prints require no enhancement in order to be viewed, because they are impressed onto an object and are easily observable.
LATENT PRINTS - are fingerprint impressions secreted in a surface or an object and are usually invisible to the naked eye. These prints are the result of perspiration which is derived from sweat pores found in the ridges of fingers. When fingers touch other body parts, moisture, oil and grease adhere to the ridges so that when the fingers touch an object, such as a lamp, a film of these substances may be transferred to that object. The impression left on the object leaves a distinct outline of the ridges of that finger. These fingerprints must be enhanced upon collection and, because they serve as a means of identifying the source of the print, they have proven to be extremely valuable over the years in the identification of its source.

Now that we have categorized the various types of fingerprints, let's determine if we were crime scene investigators, could we differentiate among the fingerprint types? If you were a crime scene investigator or an investigator of a scene of interest, what type of fingerprints would you have discovered in these cases?
  1. A Hershey's chocolate bar
  2. A bloody print on a knife
  3. A baseball helmet
The correct answers are:
  1. Plastic prints because the chocolate bar softens when held and the ridges of the finger are present and visible to the naked eye.
  2. Patent prints because a foreign substance, namely blood, has left a visible impression on an object, namely the knife, which is visible to the naked eye.
  3. Latent prints because the helmet must be examined and the surface of the helmet technologically enhanced in order for the fingerprints to be viewed. Some techniques available to provide for identification of these types of prints are lasers, powders and various light sources.
The knowledge of the different types of fingerprints is invaluable to investigators in their quest to identify the source of the fingerprints, and the science of fingerprints is fascinating to the lay person. For investigators, fingerprints can provide invaluable clues as they serve as a means of identifying the source of the print. Because the seasoned investigator has a thorough knowledge of the different types of fingerprints, he is able to recover them for use as evidence or for other purposes.