January 1999

The Tide of Prints

Continued from page 3

By Eric Scigliano

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Another question: just whose search system is this? IAFIS will be overwhelmingly weighted toward the ten-print searches that police and courts care most about-background checks run on prints taken from the people they stop, book and sentence. But it may not do as much for the smaller cohort of investigators trying to solve crimes with latent prints. Nowadays, detectives typically don't dust for prints after burglaries; their states' crime labs are too overloaded to trace them. If they expect a change under IAFIS, warns Ed German, the Army Crime Lab's senior special agent, "many police departments are going to be very surprised."

IAFIS promises to match only 635 latent crime-scene prints a day, even as it conducts 60,000-plus ten-print searches. This was no oversight, but a deliberate allocation of resources. The Advisory Policy Board urged against building a large latent-search capability into the national system because most such searches involve local offenders. And the 635 promised latent searches will consume much more computing power than all the ten-print searches combined. Because a ten-print's origins are known-say, "white female left index finger"-the search engine can concentrate on the pertinent section of its database. And because ten-prints are crisp and complete, it can compare them with the digital equivalent of a quick glance. Latent prints are often smudged and incomplete, with no indication of which fingers they represent, or the race or gender of the people who left them. And since each search can penetrate only about 30 percent of the IAFIS database, the system must make multiple searches to match a single latent.