U.S. Sen. Jon Kyl, R-Ariz., a sponsor of the bill, says collecting DNA from arrestees would help authorities catch rapists and killers who have arrest records but who go undetected by the DNA system because they have no serious convictions. Barry Steinhardt, who specializes in privacy law for the American Civil Liberties Union, says taking DNA from people who "haven't been found guilty of anything" is wrong. "We've got to ask ourselves whether this is a line we want to cross."

The Senate bill would tap new DNA sources. In 2004, 235,000 suspected immigration violators were detained, the Department of Homeland Security says. The Justice Department says 124,210 people were arrested on federal charges in 2002. Since the war on terrorism began in 2001, the Defense Department says, U.S. forces have detained about 70,000. Under the Senate bill, all would be eligible for DNA testing.