Crime and Computers

By: Mark Hansen - Published in: ABA Journal
August 2002

'Digitally Enhanced' Evidence Draws Challenges From Defense

On mother's day 1995, 27-year-old Bible school student Dawn Fehring was found dead on the bedroom floor of her Seattle-area condominium. It did not take complex evidence analysis to determine she had been murdered.

Her body was found nude, lying near the foot of her bed, with her top bed sheet and a T-shirt wrapped around her head and neck. Bloodstains were found on the carpet near her body and on the fitted sheet covering the mattress. An autopsy showed she had been raped and strangled.

Police processed the crime scene for evidence and began interviewing neighbors, including a 32-year-old mill worker named Eric Hayden, who was about to become their chief suspect. Hayden, who lived upstairs and across the hall from the victim, seemed nervous during the interview and couldn't account for his whereabouts on the night of the murder, police said. He told them he had been out drinking with friends, but couldn't provide any names. He told his live-in girlfriend, who had been away for the weekend, that he was too drunk to remember where he had been.

But the crime scene yielded few clues as to the perpetrator's identity; only a handful of bloody handprints in the victim's blood on the pink fitted bed sheet. And those prints were so obscured by the color and the weave of the fabric, they couldn't be identified through conventional means - even after a chemical process that turns bloodstains a dark blue.

That's where Erik C. Berg, a pioneer in the field of digital imaging technology, comes in. Berg, a crime scene analyst and fingerprint identification expert with the Tacoma (Wash.) Police Department, had been experimenting with the use of a software program he helped develop. The software could "enhance" digital images or photographs processed through a computer, by filtering out background patterns and colors.

Berg had been waiting for a real homicide case on which to test the technology. So he took digital photographs of the bloody prints, downloaded them into a computer and filtered out the background pattern created by the weave of the fabric to make the prints stand out more clearly.

The immediate result: Two prints were positively matched with Hayden's prints, on file from an earlier DUI arrest. Hayden is now serving a 27-year prison sentence for murder.

The long-term result, and one with potentially more far-reaching impact: the first of only two published appellate court decisions to date affirming the admissibility of digitally enhanced fingerprint evidence. State v. Hayden, 950 P.2d 1028. (Wash. Ct. App. 1998). The second was an Ohio Supreme Court case that was decided last October. State v. Hartman, 754 N.E. 2d 1150.

VARYING SHADES OF CONCERN

For police and prosecutors, the use of digitally enhanced evidence is a non-issue. They say the enhancement process adds nothing to the underlying image; it only makes what is already there more usable by improving sharpness and image contrast. They argue a fingerprint is too complex to be altered digitally. And besides, they say, the software they use to enhance the image would prevent them from altering it even if law officers wanted to.

But for some defense attorneys and experts on scientific evidence, the use of digital imaging technology raises serious questions about where enhancement ends and manipulation of evidence to fit police needs begins.

John Zwerling, an Alexandria, Va., lawyer who sits on the National Association of Criminal Defense Lawyers' board of directors, says he doesn't understand how an image can be enhanced without being changed.

"If you're going to enhance a photo, it seems to me you'd have to make some assumptions and fill in some details that aren't there," he says. "Otherwise, you'd be able to see it" prior to being enhanced.