Vast DNA Bank Pits Policing Vs. Privacy

A big increase in tests would also generate more mistakes, said William C. Thompson, a professor of criminology, law and society at the University of California at Irvine, whose studies have found DNA lab accuracy to be "very uneven."

In one of many errors documented by Thompson, a years-old crime-scene specimen was found to match the DNA from a juvenile offender, leading police to suspect the teenager until they realized he was a baby at the time of the crime. The teenager's blood, it turned out, had been processed in the lab the same day as an older specimen was being analyzed, and one contaminated the other.

"A universal database will bring us more wrongful arrests and possibly more wrongful convictions," said Simoncelli of the ACLU.

But Asplen of Smith Alling Lane said Congress has been helping states streamline and improve their DNA processing. And he does not think a national database would violate the Constitution.

"We already take blood from every newborn to perform government-mandated tests . . . so the right to take a sample has already been decided," Asplen said. "And we have a precedent for the government to maintain an identifying number of a person."

While the debate goes on, some in Congress are working to expand the database a bit more. In March, the House passed the Children's Safety and Violent Crime Reduction Act.

Under the broad-ranging bill, DNA profiles provided voluntarily, for example, in a dragnet, would for the first time become a permanent part of the national database. People arrested would lose the right to expunge their samples if they were exonerated or charges were dropped. And the government could take DNA from citizens not arrested but simply detained.

The bill must be reconciled with a Senate, which contains none of those provisions.