The DNA Dragnet

Probably not. A better question might be, Do DNA dragnets work? The answer so far is, rarely. The largest sweep in the U.S. took place in Miami, where in 1994 cops sampled 2,300 men in search of a serial killer. The dragnet did not catch the killer. Of the 18 publicized U.S. sweeps, only one--a narrow sampling of 25 workers at a nursing home--has been successful, according to a 2004 study by criminologist Samuel Walker of the University of Nebraska at Omaha. Walker called the sweeps "unproductive" and said that if they are to continue, national guidelines are urgently needed.

In Britain, where the first ever mass DNA sweep took place in 1987 (indirectly leading to the conviction of a rapist and murderer who tried to escape detection by asking a co-worker to take the DNA test for him), the results have been more impressive--and the public far less resistant. The Forensic Science Service of England and Wales has carried out 292 DNA dragnets since it began counting in 1995. So far, 61--about 20% of all sweeps--have produced significant matches, helping push an investigation toward a suspect and, on numerous occasions, a conviction. In 1998 Str??cklingen, Germany, undertook the largest collection to date. More than 16,000 men in a rural town were sampled after a girl, 11, was raped and strangled. In a quest to restore the town's innocence, entire soccer teams took the test together. The killer, pressured to participate by friends, also complied, sealing his fate.

Given the history of Massachusetts' crime lab, it's hard to imagine Truro's DNA samples getting processed anytime soon. It took several months just to get the DNA from the initial suspects processed in the Worthington case. But D.A. O'Keefe insists, without elaborating, that the effort will have "ancillary benefits." The rush of attention has clearly got the town talking again.

And maybe, somewhere, it has got someone nervous, says Chief Thomas. "I hope that whoever did this cannot sleep at night. And if they do sleep, I hope they have nightmares. I hope they wake up in a cold sweat. And I hope the person next to them realizes what's going on and says something." --With reporting by Theunis Bates/ London, Marc Hequet/St. Paul and Ruth Laney/ Baton Rouge