Page 79 - Automated Fingerprint Identification Systems (AFIS)

64 AUTOMATED FINGERPRINT IDENTIFICATION SYSTEMS

million records may be much fewer than six billion, but it is a good represen-
tative sample and a good test. So to the question “Can it be scientifically
proved?” the response is “Not in the immediate future.” But there are other
indicators.
AFIS systems have been around for over 20 years. Their matchers have
compared millions of finger images. The FBI has 46 million records yet has
not found any case where an identical image belongs to two different people.
In 1999, the Latent Print Section of the FBI sent latent prints to several
state identification agencies asking for a latent print search against the state
database. There were no finger images identified that did not belong to the
target.

3.5.3 IMAGE QUALITY

Tenprint applications require an image with detail sufficient for extracting the
image feature characteristics of minutiae, direction of ridge flow, patterns, etc.
Finger images may be categorized as missing, bandaged, poor quality, fair
quality, or good quality. A missing finger means that the finger could not be
printed, most probably because it had been amputated. Unlike missing fingers,
bandaged fingers may appear on some tenprint records of the subject and not
on others. If a person was printed as part of a job application and one finger
was bandaged, it would be noted on the record. If the same person was fin-
gerprinted later with the bandage removed, the record would be updated with
the image from the previously bandaged finger. The newly captured image
would become part of the person’s image record, resulting in a complete set
of ten rolled images. Because some AFIS systems search on multiple image
records for the same person, this person may have a set of 19 images: nine from
the first fingerprinting and ten from the second.
Following the direction of the identification agency managers, AFIS coders
categorize fingerprint images as poor, fair, or good quality. These categories are
generally determined by the number of minutiae extracted from a finger image.
A poor-quality image may initiate a request to re-roll the subject, if possible.
Any subsequent records of that person would be checked for improved quality
of the images. Fair-quality images have image detail sufficient for identification
but should be replaced with good-quality images in the future if possible.
Good-quality images meet or exceed the standard for image quality. There is
clear ridge detail and flow, and a large number of minutiae.
If an inked print is taken with careful attention to detail, using either a prop-
erly maintained livescan machine or a standard printer’s ink and approved
tenprint card stock, the images will be clear, assuming no dermatological prob-
lems. A great amount of detail will be captured and will be available for subse-