The Automated Fingerprint Identification System

In the early days of fingerprinting law-enforcement agencies began "booking" fingerprints taken from individuals arrested for crimes so that the records would be readily available. They also began to maintain leftover latent prints so that they might be compared with existing and future additions to the fingerprint files.

The first law-enforcement agencies to develop fingerprint collections were large ones, such as the NYPD, LAPD, and FBI. These agencies sponsored rigorous research into how best to carry out scientific comparison of fingerprints. They subsequently developed strong training programs for maximum efficiency. Nevertheless, the sheer numbers of fingerprints flowing into these departments soon overwhelmed them. These agencies had rooms full of filing cabinets crammed with fingerprint cards. Without the Henry system of classification the task of cataloging and organizing the fingerprints into any kind of usable file would have been hopeless.

The traditional method for processing a new fingerprint card was to classify each of the 10 fingerprints of the individual, then search the files for a duplicate card, if any. Once it was determined that the prints were "new," the next step was to compare them to the file of latent prints from unsolved cases. A fingerprint examiner might spend hours with these tasks. The process was even more laborious if a single latent print, without the remaining fingerprints of the hand to help narrow the field, was brought in for identification, because many more comparisons would be needed.

The pressure of case demands combined with the tedious and time-consuming process of manual comparison made for a very undesirable work environment. All this prompted agencies to look for some relief in the form of automation through electronic media and digital imaging. The tremendous success of fingerprint identification technology has ushered in a whole new era in law enforcement, to say nothing of turning a boring job into a high-tech profession.

An AFIS works like this: A latent fingerprint that cannot be defined as to which hand (left versus right) or finger comes into the fingerprint unit. The fingerprint examiner scans and enters the fingerprint into the system. The software then compares the fingerprint with all the fingerprints in the system. If the software finds one or more possible matches, it reports them in descending order of probability, that is, the most likely candidate is reported first and the less like candidates follow in the listing. The first diagram shows the flow of a fingerprint through the fingerprint identification process, including AFIS.

This automation cuts out a huge amount of labor for the fingerprint examiner, but it does not eliminate his or her job. The actual identification at the end of the process must be carried out by the examiner, not by the machine. The machine is not capable of making the final judgment, which must be based on experience and training as well as visual appearances. At the beginning of the process, too, only human expertise will do. Before it can be put into the system, the latent print must first be evaluated as to whether it is "AFIS quality," which requires visual evaluation by the examiner. If enhancement is appropriate, the examiner must perform this as well.

As shown in the second diagram, the AFIS consists of three steps or stages: data sensing (of the fingerprint), data extraction (of the sensed

Afis Flow Diagram

© Infobase Publishing

The flow of a fingerprint through the fingerprint unit

© Infobase Publishing

The flow of a fingerprint through the fingerprint unit

Automated fingerprint identification system (AFIS) flow chart data), and comparison evaluation (the machine evaluates the quality of the "match"). The AFIS may be set to accept or reject a certain threshold of comparison quality. In this way the examiner can increase or reduce the number of possible matches the machine offers.

It is important for the reader to understand that AFIS is a process and not a particular brand name of equipment. There are a number of manufacturers of AFIS equipment, and different manufacturers rely on different systems for comparison. For example, one system may base identification on multiple impressions of the same finger, while another uses multiple different fingers of the same hand. The quality of the AFIS systems currently on the market has improved dramatically over the years. At its inception AFIS were stand-alone systems that could not communicate with one another. If two neighboring agencies purchased AFIS equipment from different manufacturers, each was unable to search the other's database (a problem analogous to the PC-Macintosh situation). This has changed somewhat, making communication between different systems more feasible.

A continuing problem is data storage. Too much data in AFIS, like too much data in a personal computer's hard drive, causes the system to become sluggish. As with written data, compression of fingerprint images is the first solution. There has been some success with this, but research is currently being done to improve matters.

Most of the problems associated with AFIS comparisons, however, can be attributed to the data acquisition step. This is the old "garbage

6 Infobase Publishing in equals garbage out" problem. Recall that the friction ridge detail of a person's hands is three-dimensional: It has length, width, and depth. Fingerprinting, however, does not record depth, and scanning methods affect the consistency of the two-dimensional image that is recorded. One method of entering fingerprints into the database is through live scanning, where the fingers are pressed directly onto a glass plate. Slight differences in pressure of the finger can cause apparent changes in the appearance in two dimensions. Likewise, nonuniform contact can cause distortion. Cuts, burns, and other damage, either temporary or

All humans make mistakes; however, there is zero tolerance for mistakes in forensic science. How then can humans be involved? The resolution to this apparent paradox is a system of checks, balances, and strict guidelines. With fingerprint identification a key requirement is that all identifications must be verified by another examiner. But does that always work? The answer is most of the time, but not always, as the following story illustrates.

On March 1 1, 2004, terrorist bombings in Madrid, Spain, killed 1 91 people and injured 2,000. An investigation produced a plastic bag containing the detonator, and latent fingerprints were recovered from the plastic bag. The Spanish National Police provided the FBI with photographic images of the latent fingerprints, and the FBI lab in Quan-tico, Virginia, used AFIS to search 4-5 million print records for possible matches to the fingerprints. One of the fingerprints was linked by AFIS to a Portland, Oregon, lawyer named Brandon Mayfield, as reported in the Oregonian newspaper.

According to the regional news Web site OregonLive.com, the FBI had asked Spanish authorities for the original evidence when the digital images first arrived in March 2004 but got no response. The FBI proceeded with the comparison, and ultimately an FBI examiner determined that the print belonged to Mayfield. At least three additional

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Responses

  • aatos
    What is afis and its flow sheet diagram?
    7 years ago
  • hamid
    How have Automated ID Systems changed forensic science?
    5 years ago
  • MARCHO
    What scientist evaluates fingerprints?
    5 years ago
  • stefan ven
    What is afis in forensic science?
    5 years ago
  • jonne
    How does magnetic fingerprint and automated fingerprint identification help forensic scientist?
    4 years ago
  • Cora
    How are fingerprints put into AFIS SYSTEM?
    3 years ago
  • Michael
    What is AFIS related to forensic science?
    2 years ago
  • Petra P
    What is iafis in forensic science?
    2 years ago
  • Michelino
    What is the AFIS how would forensic scientist use it?
    2 years ago
  • felix
    What was the contribution to forensic science the afis and iafis?
    1 year ago
  • mhret
    When is your data put into afis?
    1 year ago
  • milena ambessa
    How does AFIS work 2014?
    4 months ago
  • galileo
    How does afis system work?
    3 months ago
  • pamphila
    How much is magnetic fingerpritinging and automated fingerprint?
    2 months ago
  • NOORA UPPA
    How does afis classify fingerprints?
    2 months ago
  • ramiro
    How does afis compare fingerprints?
    2 months ago

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