CLARKSBURG, W.Va. -In a sprawling complex tucked in the hills of this Appalachian town, a roomful of supercomputers attempt 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 less than 30 minutes - something that used to take 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 speed up such checks over the past few years has created the risk of accusing people who are innocent, the Chicago Tribune has found.
Across the country, police departments and crime labs are submitting fingerprints for comparisons and 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 the typical digital camera, a digital fingerprint provides less complete detail than a traditional photographic image. That 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.
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 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 FBI director at Clarksburg.
Such confidence is unwarranted, according to digital-imaging specialists and some leading fingerprint experts. They say the potential for mistakes is growing inexorably as police departments around the nation switch from old inked cards to digitized computer images.
"It gives examiners the misleading impression that they're getting a better quality image to examine," said Michael Cherry, an imaging expert who is on the evidentiary committee of the Association for Information and Image Management, a business technology trade group. "These images actually can eliminate fingerprint characteristics that might exclude a suspect."
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 whether the fingerprint image entered into evidence has been digitized.
"I think it's a very real problem, but it's under the [radar] still," said Mary Defusco, director of training at the Defender Association of Philadelphia, a nonprofit group that represents indigent defendants. "We have to get up to speed on it."
One of the nation's first successful challenges to the use of digital fingerprinting in the courtroom came last year in Broward County, Florida.
The only physical evidence linking Victor Reyes to the murder 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," that has long been used in traditional photography.
Reyes' attorney, Barbara Heyer, argued such digital enhancements were inappropriate manipulations of the evidence. "It just hasn't gotten to the point of reliability," Heyer said.
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. The jury foreman, Richard Morris, who happens to write computer-imaging software for a living, said in a recent interview that he and his fellow jurors had significant concerns about it.
"The makers of the [Adobe] software dropped the ball in not providing a digital record of every action applied to the image," Morris said. He said he would like to see lab analysts or police personnel use software that automatically logs any changes so that other examiners could come back later to determine whether the digital print had been inappropriately altered.