AFIS (Automated Fingerprint Identification Systems) allows law enforcement agencies to conduct applicant and suspect fingerprints with literally thousands or millions of file prints in a matter of minutes. A manual search of this nature would take hundreds of hours with little hope for and less chance of success. The heart of AFIS technology is the ability of the computer equipment to scan and digitize fingerprints by reading spacing and ridge patterns and translating them into the appropriate computer language coding. The computer is capable of making extremely fine distinctions among prints, lending further accuracy and reliability to the system.
The computer can map 90 or more minutia points (ridge endings, bifurcations, directions, and contours) for each finger. This is a number high enough to individualize a fingerprint and distinguish it from all others. Latent prints normally do not have 90 minutia points, but matches usually can be made with as few as 15-20 minutia points.
Technicians can computer-enhance fingerprints when preparing them from a search. This process enables an experienced technician to fill in missing or blurred portions or print fragments or to correct for breaks in patterns or ridges caused by burns or scars.
The computer translates patterns into mathematical computer codes. The computer is not comparing images of a suspect's prints against images of known prints rather, it is conducting a mathematical search that can compare a subject print against file prints at a rate of up to 600 points per second. Search time will vary depending on such factors as preparation time, demographic data that are entered to limit the prints required to be searched, the size of the file, and the number of key factors, or matches, being used to seek a match. A latent print can be searched against a file of 500,000 prints in about half an hour.
Although the accuracy of the AFIS system is 98 to 100 percent, this does not mean that the computer makes positive matches that percentage of the time.