A Trial of High-Tech Detectives

By Dick Thompson/Washington

A technique called DNA fingerprinting has, since the mid-1980s, become an important tool for police and prosecutors. Matching a suspect's DNA, the genetic material found in most cells, with DNA found in blood or semen at the scene of a crime can provide seemingly indisputable evidence of guilt. But now DNA fingerprinting is itself on trial, and shadows of doubt are falling on detective work that once seemed virtually infallible. Says William Thompson, a professor of social ecology at the University of California at Irvine: "This technology has been steamrollered through the courts, and now it's beginning to get serious scrutiny."

At the center of the controversy is a pretrial hearing that ended last week in the same Bronx, N.Y., courthouse that was depicted in Tom Wolfe's best seller The Bonfire of the Vanities. Joseph Castro, a 38-year-old janitor, stands accused of killing a neighbor and her two-year-old daughter. According to the prosecutors, a portion of DNA extracted from a spot of blood on Castro's watch matched DNA taken from the murdered mother. The chance of such a match occurring at random, said scientists called by the prosecution, was 1 in 100 million.

But the defense enlisted scientists of its own to review the evidence. A panel of experts from both sides eventually agreed that the evidence presented was "not scientifically reliable enough." They did not say the DNA analysis was invalid but asserted that in this case it was not nearly so precise as the prosecution claimed. One expert calculated that there was a 1 in 78 chance that the blood on Castro's watch was not from the victim. That may be a small chance, but to the defense it constituted a distinct shadow of a doubt.

The judge in the Castro case is expected to rule in June on the admissibility of the DNA test as evidence. His decision could have reverberations across the U.S., since evidence from DNA analysis has led to dozens of convictions and helped put at least two men on death row. Now many of these cases may have to be re-examined. Says Randolph Jonakait, a professor at New York Law School: "((The Castro case)) is a bombshell in DNA litigation."

Advocates of DNA fingerprinting still maintain that the tests are practically foolproof if done properly. "It's not the technology that's being challenged," says John Hicks, a deputy assistant director of the FBI, "but the proficiency of the tester." Unlike traditional fingerprinting, which is done by police experts in official labs, DNA testing is carried out by several private firms that specialize in the technique, and the courts have no direct control over the quality of the work. The tests in the Castro case were performed in 1987 by the oldest and largest company in the business, Lifecodes of Valhalla, N.Y. The firm insists that it has refined its methods in the past two years.

Still, Lifecodes and other DNA-testing companies say they would welcome official standards for their laboratory procedures. Such standards are being developed by the FBI, along with several state governments. If this new industry is adequately regulated, then DNA fingerprinters could once again become reliable witnesses instead of suspects.