Convicted by Their Genes

By Anastasia Toufexis

Jurors at the trial of Victor Lopez were troubled by a major discrepancy. Lopez, charged with sexually assaulting three New York women, is a light- skinned Hispanic, yet each of the women had told police that her assailant was black. Was he, as his attorney insisted, a victim of mistaken identity? No, concluded a jury in Queens, N.Y., last week; it found Lopez guilty of all three attacks.

Billy Lewis Glover Jr. had been tried twice for rape, but both Dallas proceedings had ended in mistrials. Earlier this month a third jury took just 22 min. to return the verdict -- guilty.

The pivotal evidence was the same in both cases: results from a new forensic test, known as DNA, or genetic, "fingerprinting," which can specifically match a suspect to genetic material in blood, hair or semen left at the scene of a crime. Hailed as the single greatest forensic breakthrough since the advent of fingerprinting at the turn of the century, the technique is being put to use with growing frequency in the nation's courtrooms. Orlando prosecutors scored the first conviction in the U.S. based on DNA typing just last November in a rape trial; since then it has figured prominently in more than 150 cases in eleven states.

Advocates claim the test will revolutionize the investigation of violent crimes, from rapes and homicides to armed robberies. It also promises to resolve questions of kinship, a matter of import in child-support and immigration disputes, and will provide a reliable new means of identifying human remains.

In more than 1 million criminal incidents each year, suspects are not even arrested because evidence is too weak. "With DNA printing," boasts Robert Shaler of Lifecodes in Valhalla, N.Y., one of three U.S. companies that offer the analysis, "police will now be able to say with certainty, 'That's the guy,' instead of 'That could be the guy.' "

Older biochemical tools, which have progressed from simple blood typing to analyzing specific enzymes and proteins, are crude by comparison. With the best combination of such methods, the chance of making a matching error is one in 1,000. DNA, however, is unique for each individual, and a matchup between a crime-scene sample and material obtained from the accused (usually in a blood sample) is virtually unassailable, say experts. Declares John Huss of Cellmark Diagnostics in Germantown, Md., another DNA-testing firm: "Except for identical twins, one in 4 trillion or 5 trillion people might share the same genetic fingerprint."

The technique not only helps place the suspect at the scene of the crime, but can also suggest what he or she was doing there. "One may have some plausible explanation for fingerprints," explains Timothy Berry, a prosecutor in Orlando. "But blood, semen, uprooted hair, skin under the fingernails of the victim are something else." The information can be so damning that it precipitates a confession. In Tacoma last December, a bus driver pleaded guilty to rape, although the victim, a 57-year-old woman with Alzheimer's disease, does not remember the crime. DNA analysis established that semen on the woman's undergarments belonged to the accused. On the other hand, genetic fingerprinting can be equally powerful in establishing a suspect's innocence.

Still, DNA printing is not yet automatically acceptable in court as evidence. Judges now rule on its admissibility on a case-by-case basis. But the methodology, which has long been used in biological research, is expected to survive legal challenges, and the FBI is moving rapidly to adopt the technique.

Ultimately, forensic experts foresee the creation of computerized banks of DNA prints. Washington State's King County is wasting no time. Beginning in January, the county plans to take DNA samples from all convicted sex offenders. The aim: a DNA library that will pinpoint the owners of genetic fingerprints left at the scenes of future crimes.

With reporting by Thomas McCarroll and Raji Samghabadi/New York