Washington ? Another arrest in a high-profile crime, another pullback by the FBI.

The release of Oregon lawyer Brandon Mayfield after the FBI acknowledged it had mistakenly matched his fingerprint to one found near the scene of the deadly Madrid train bombings is the latest illustration of what critics say is a flawed U.S. anti-terror policy that threatens Americans’ civil liberties and privacy.

“It underscores the dangers of this kind of policy of arrest first, ask questions later,” David Cole, a Georgetown University law professor and critic of post-Sept. 11 law enforcement tactics, said Tuesday.

The FBI made a rare apology to Mayfield on Monday night, after the Kansas native was cleared of any connection to the March 11 bombings that killed 191 people and injured more than 2,000. FBI officials said Tuesday they would have no further comment.

To critics of government anti-terrorism tactics, Mayfield’s arrest shows that the government is far too willing to detain people with little evidence.

Mayfield was taken into custody on a material witness warrant, a law that has been on the books for decades to allow prosecutors, with a judge’s approval, to detain people so they can testify when there is a reasonable fear they might flee.

“It’s an easy tool for the government to use to detain someone when they don’t have evidence of a crime,” said Anjana Malhotra, an attorney with the American Civil Liberties Union.

The Mayfield case, Malhotra said, “is a classic example of the government’s misuse of the material witness warrant.”

Justice Department and FBI officials reject that characterization, although ultimately no charges were brought. The FBI said the Spanish bombing fingerprint linked to Mayfield “was based on an image of substandard quality.”

It wasn’t until after the FBI sent two fingerprint examiners to Madrid to examine the physical evidence in person that it became clear the print was not a match to Mayfield.