CLARKSBURG, W.Va. - Deep inside a sprawling complex tucked in the hills of this Appalachian town, a room full of supercomputers attempts to sift America's guilty from its innocent.
This is where the FBI keeps its vast database of fingerprints, allowing examiners to conduct criminal checks from computer screens in fewer than 30 minutes - something that previously took them weeks as they rummaged through 2,100 file cabinets stuffed with inked print cards.
But the same digital technology that has allowed the FBI to so drastically speed such checks over the last few years has created the risk of accusing people who are innocent.
Across the country, police departments and crime labs are submitting fingerprints for comparisons and for entry into databases, using digital images that might be missing crucial details or might have been manipulated without the FBI knowing it.
Not unlike a picture from a typical digital camera, a digital fingerprint provides less complete detail than a traditional photographic image. That matters little with pictures from the family vacation. But when the digital image is of a fingerprint, the lack of precision raises the specter of false identifications in criminal cases.
"There's a risk that not only would they exclude someone incorrectly - we have the potential to identify someone incorrectly," said David Grieve, a prominent fingerprint expert who is the latent prints training coordinator for the Illinois State Police crime lab system.
An FBI-sponsored group of fingerprint examiners was concerned enough about the quality of digital images that in 2001 it recommended doubling their resolution. Three years later, though, the vast majority of police agencies still use equipment with the lower resolution.
Equally troublesome, the most commonly used image-enhancement software, Adobe Photoshop, leaves no record of some of the changes police technicians can perform as they clean up fingerprint images to make them easier to compare.
This seemingly esoteric issue is crucial because it raises questions about a bulwark of the criminal justice system: chain of custody. If authorities can't prove a fingerprint is an accurate representation of the original and show exactly how it was handled, its validity can be questioned.
FBI officials recognize the resolution problem, but say it leads to overlooking guilty individuals, not falsely accusing the innocent. "The risk that we're hearing is that we miss people - because the resolution isn't enough - not that we're identifying people incorrectly," said Jerry Pender, deputy assistant director at the FBI's Clarksburg facility.
Such confidence is unwarranted, according to digital-imaging specialists and some leading fingerprint experts. And they say the potential for mistakes is growing inexorably as police departments around the nation switch from old inked cards to digitized computer images.
To do so, technicians scan an inked card into a computer, which converts it into a pattern of 0's and 1's that digitally represent the image, similar to how a fax machine works. And, like a fax machine, the process of digitizing the fingerprint loses considerable amounts of detail.
Measuring the number of cases where a digital image might have wrongly linked a suspect to a crime scene is difficult. The technology is so new that many defense attorneys don't know to ask if the fingerprint image entered into evidence has been digitized.
One of the nation's first successful challenges to the use of digital fingerprinting in the courtroom came last year in Broward County, Fla.
The only physical evidence linking Victor Reyes to the killing of Henry Guzman was a partial palm print - an intriguing trace of evidence found on duct tape used to wrap the body in a peach-colored comforter.
A forensic analyst with the Broward County sheriff's office used a software program known as MoreHits along with Adobe Photoshop to darken certain areas and lighten others - a process called "dodge and burn," which has long been used in traditional photography.
Reyes' attorney, Barbara Heyer, argued such digital enhancements were inappropriate manipulations of the evidence.
Jurors acquitted Reyes, largely because of sloppy handling of the evidence by police. But they also were troubled by the digital fingerprinting technology used in the case.
Ten years ago, only a handful of major police departments used digital fingerprinting. Today, more than 80 percent of the prints submitted to the FBI's Clarksburg facility are digital.
Along with the digital technology has come inexpensive software that allows personnel at stations to enhance the prints at their desks. One of the most widely used digital-print software programs, MoreHits, claims about 150 clients among local, state, federal and foreign law enforcement agencies.
Defenders of the technology contend that concerns about it are overstated because computers only spit out a list of potential matches; typically, human fingerprint examiners at the FBI's lab and at state crime labs make the final matches introduced in court.
Asked last month about the questions involving digital prints, the FBI issued a statement saying it would not comment further until eight teams of forensic scientists finish "methodically inspecting every aspect of the latent fingerprint process, which includes the examination of digital images."
The Chicago Tribune is a Tribune Publishing newspaper.