Fingerprinting - an Emerging Technology
by Debbie Salter

dsalter@nmsu.edu

Engineering Technology 357

New Mexico State University

Over the past few years, as society has grown, the crime rate has also increased. Politicians, law enforcement personnel, criminal justice experts, and numerous other people have not only tried to explain the cause for this increase but also have tried to find ways to combat this problem. One way that experts have begun to combat this problem is through automated fingerprint identification technology.

BACKGROUND

In the United States, the first systematic and official use of fingerprints for personal identification was adopted by the New York City Civil Service Commission in 1901. The method was used for classification of civil service applications. In 1924, the fingerprint records of the Bureau of Investigation and Leavenworth Prision were merged to form the nucleus of the identification records of the new Federal Bureau of Investigation. Presently, the FBI has the largest collection of fingerprints in the world. [1]

FINGERPRINT IDENTIFICATION IS BASED ON THREE KEY PRINCIPLES:

A fingerprint is an individual characteristic;

Fingerprints remain unchanged during an individual's lifetime;

Fingerprints have general ridge patterns that permit them to be systematically classified[2]

In forensic work, the use of fingerprints is important for several reasons. First, prints have a wide variation since no two people have identical prints. Second, there is high degree of consistency. A person's fingerprints may change in scale but not in relative appearance. Fingerprints are left each time the finger contacts a surface.

THERE ARE THREE MAIN GROUPS OF FINGERPRINTS:

  • Plastic fingerprints - these occur when the finger touches or presses against a plastic material in such a way that a negative impression of the friction ridge is produced. These types of prints are generally found in places like a newly painted object, wax from candles or sealants, in the gum on envelopes and stamps, on substances that melt easily or soften when they are held in the hand. An example of this would be chocolate.
  • Prints which are contaminated with foreign matter usually containing dust - these prints occur when fingers are pressed in a thin layer of dust and some dust sticks on the friction ridges. When the finger touches something else, a print is identifiable.
  • Latent fingerprints - these result from small amounts of grease, sweat, and dirt being deposited on the object touched from every detail in the friction ridge pattern at the tip of the finger. [3]

    • METHODS FOR DETECTION OF FINGERPRINTS
  • Plastic prints and prints that are impacted on an object are easily detected since they are visible to the naked eye
  • Latent prints are developed using a variety of methods. One is the dusting of powders over the prints. Another method is using iodine since this discolors the print. Lasers may also be used to detect latent prints. The laser light has been discovered to produce florescent fingerprints which can be photographed. [2] A fingerprint examiner, wearing safety goggles containing optical filters, examines the specimen being exposed to laser light. The filter absorbs the laser light and permits the wavelengths at which latent print residues fluoresce to pass through to the eyes of the wearer. [1] Some forensic crime labs use image processing, in which latent prints are examined by a video camera and a signal is fed into a computer which processes the image.[3]

    HOW THE PROCESS OF AUTOMATED FINGERPRINT TECHNOLOGY WORKS

    The typical fingerprint may have as many as 150 ridge characteristics. The ridge characteristics of the finger are formed where the epidermis (the outer portion of the skin) and dermis (the inner skin) meet. Perspiration, salts and skin oil on the fingertips combine to leave a pattern on any surface where the skin touches. [2] In the past, individual prints were compared to prints on file by fingerprint examiners. New technology enables computers to do this work. Computers are able to scan and digitally encode fingerprints so that they can be subject to highspeed computer processing. Automated fingerprint identification uses automatic scanning devices that convert the image of a fingerprint into digital minutuae (the ridge characteristics) that contains data showing ridges at their points of termination (ridge endings) and the branching of ridges into two ridges (bifurcations). [1] The scanning converts the spatial relationship of a fingerprint's ridge endings and ridge bifurcations called minutiae points into a digitized representation of the fingerprints. [4]

    The process of automated fingerprinting works by scanning fingerprints and storing them digitally in a computer's memory. The computer then creates a spatial map of the unique ridge patterns of the prints and then translates this spatial relationship into a binary code for the computer. As new fingerprints are scanned into the computer, the computer searches for any identical prints and updates the system. This enables law enforcement agencies to identify criminals more quickly and also have access to a large data base with information on fingerprints. This alone has greatly enhanced the efficiency of the criminal justice system and also increased the conviction rate for offenders.

    The most interesting part of this new system is the sophistication and intricacy of the scanning for the computers. Humans are not always able to identify prints with this much accuracy. Many agencies do not have the enough people to be able to search and file all the prints. They also do not have the people to compare all the prints and try to find matches. Computers have provided a link to helping law enforcement officials apprehend criminals and also protect those who are unjustly accused. Officals are able to enter a print into the computer and have the computer search for matches. The computer also analyzes the print for any specific markings.

    • Computers now provide the following abilities:

  • Enable law enforcement officials to spend more time investigating suspects generated by the computer versus developing suspect lists [1]
  • Scan fingerprint impressions
  • Automatically identify characteristics with enough detail for identification of a single print amoung thousands
  • Accuracy of this search is as high as 98-100%
  • Elimination of time issues and human error in classification and comparision
  • Enhancment of speed and accuracy of fingerprint comparisons
  • Able to identify and classify more information than the capabilities of humans
  • Able to identify minute parts of fingerprints for use in courts for prosecution
  • A link for law enforcement officials to communicate with one another to apprehend criminals within different jurisdictions [4]

    • Fingerprint Technology may be use for:

  • The evidence needed for apprehension and conviction of criminals
  • To prove innocence for individuals unjustly accused of crimes
  • Identification of individuals
  • Fingerprints for employment or licensing applications. [4]

    It has been estimated that fingerprints are left at scenes of more than a third of all crimes. This is especially true for property crimes. Automated fingerprinting can help in these areas by providing a data base for prints of thousands offenders. In law enforcement agencies where the scanning has been implemented, identification rates have increased dramatically. Officials are able to enter new prints while at the same time searching for any matches of prints already in the computer. This helps law enforcement because they may stumble upon a match of prints and not ever had suspected that individual for the crime.

    Fingerprints provide a solid way of apprehending criminals and also proving innocence to those who deserve it. As new technology emerges, almost all fields in Criminal Justice are affected. Fingerprinting allows law enforcement officials to trace individuals not only in their jurisdication but in others as well. This will help to allow law enforcement agencies to communicate with one another and help each other solve crimes across the United States.

    References

    [1] Saferstein, Richard. (1995) Criminalistics: An Introduction to forensic science. New Jersey: Prentice Hall.

    [2] Kaci, Judy Hails. (1995) Criminal Evidence. Nevada: Copperhouse Publishing.

    [3] Palmiotto, Michael J. (1994) Criminal Investigation. Chicago: Nelson Hall.

    [4] Report of Automated Fingerprint Identification Systems by the Bureau of Justice Statistics.