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," which has long been used in traditional photography.
Reyes' attorney, Barbara Heyer, argued that 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 writes computer-imaging software for a living, said in a recent interview that he and his fellow jurors had significant concerns about it.
No record of image changes
"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 would log any changes so other examiners could determine later whether the digital print had been altered inappropriately.
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 many police 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.
The creators of these explosively popular tools also recognize the potential problems.
"It's like a hammer. It's not evil unless someone who is evil picks it up and uses it," said Erik Berg, a forensic expert with the Police Department in Tacoma, Wash., who developed MoreHits.
Human element crucial
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.
"The benefits to law enforcement with digital fingerprints are incalculable in terms of speed of identification and exoneration of the innocent," said Joseph Bonino, former chairman of the FBI's advisory policy board for the Criminal Justice Information Services division in Clarksburg. "They provide a high degree of accuracy, assuming your human examiners are properly trained."
Trust in that safeguard took a major hit last spring when the FBI falsely linked an Oregon lawyer, Brandon Mayfield, to terrorist bombings at Madrid train stations.
When Spanish authorities connected the Madrid print to an Algerian man, the FBI had to admit it erred.
The bureau initially blamed the quality of a digital fingerprint image forwarded from the Spanish National Police. An international panel of experts later concluded that the digital image was fine; instead, the panel found, several veteran FBI examiners had missed "easily observed" details that excluded Mayfield.
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--appointed after the Mayfield case unraveled--finish "methodically inspecting every aspect of the latent fingerprint process, which includes the examination of digital images."
The sleek computer equipment inside the bureau's facility in Clarksburg cannot negate this disturbing fact: The FBI does not know if a police agency has altered any of the thousands of new fingerprint images added every day to its database, which now has 48 million sets of prints.
As long as the submissions meet FBI standards on resolution, size and information about the subject, "we wouldn't have any concerns about the quality of images coming into IAFIS," said Steve Fischer, spokesman for the Clarksburg facility, referring to the FBI's Integrated Automated Fingerprint Identification System.
But Fischer acknowledged that those standards are not a safeguard against improper manipulation of the images.
"If they were doing something out there," he said, "we wouldn't know about it."
The broader concern, though, remains the quality of the digital images themselves. An FBI-sponsored scientific working group of fingerprint experts cited concerns about the quality of digital images in 2001, when it recommended doubling their resolution, from 500 pixels per inch to 1,000.
But that is only a guideline, and most police departments haven't invested in newer equipment that would upgrade the digital images.
"The quality of the detail . . . in the [lower-resolution] digital image is not sufficient to support a lot of what fingerprint comparisons rely on," said Alan McRoberts, chairman of the working group and editor of the Journal of Forensic Identification.
The roots of using digital images for crime-solving date to the early 1970s, when San Diego police brought a palm print image to the Jet Propulsion Laboratory in Pasadena, Calif., in the hope that scientists could enhance it.
Police had found a bloody palm print on a bedsheet at a murder scene, but the weave of the sheet obscured the print's detail. The lab's scientists managed to separate the print from the bedsheet's weave using a process similar to one employed to enhance photographs taken of the moon and planets.
Since then, the drop in prices for such technology has made it widely available to law enforcement, but critics question whether all police staffers using it fully understand its limitations.
One solution to the problem is simple, according to imaging experts: Have defense attorneys ask the right questions.
Berg, the developer of the MoreHits software, outlined them: "If this is a digital image, has it been enhanced or is this the original capture with no changes to it? If it's been enhanced, I want you to show me what you did and tell me what your training is. And did you go out of your area of expertise to do this?"
If those questions aren't asked, Berg noted, a false identification might not be caught.