The Justice Department's internal watchdog on Friday faulted the FBI for sloppy work in mistakenly linking an Oregon lawyer, a Muslim convert, to the 2004 Madrid train bombings but said the government did not misuse the anti-terror Patriot Act against him.

FBI fingerprint experts probably were more resistant to re-examining their conclusion that Brandon Mayfield's fingerprint matched one found on a bag containing detonators like those used in the attacks in Spain because of his religion, Inspector General Glenn Fine said in the executive summary of a 273-page report that otherwise remains classified.

Rejecting assertions by Mayfield and others, he said, "We did not find any evidence that the FBI misused any of the provisions of the Patriot Act in conducting its investigation."

Mayfield is suing the government, alleging he was singled out because of his Muslim faith. Mayfield's lawyers did not immediately comment on the report.

Fine said Mayfield's adherence to Islam played no role in the initial, erroneous determination that there was a fingerprint match, noting that the experts did not know Mayfield's religion, his marriage to an Egyptian immigrant or his legal representation of other Muslims.

Mayfield was arrested in May 2004 on a material witness warrant. He was released a few weeks later after the FBI admitted it had made a mistake and that the fingerprint did not match Mayfield's.

The FBI has maintained the error was due to the low resolution of the print. Fine disagreed, saying the examiners were overconfident, despite differences between Mayfield's prints and the one on the bag.

The FBI first matched the prints on March 19, eight days after the bombings that killed roughly 200 people and injured more than 1,400 others.

As a result, the FBI put Mayfield under 24-hour surveillance, and won approval from a secret court to listen to his phone calls and surreptitiously search his home and law office, Fine said.

The report also includes a brief section that suggests the FBI used National Security Letters to obtain information about Mayfield. Most of the section, titled National Security Letters, has been blacked out because the issuance of these demands for information without a judge's approval is supposed to be secret.

In mid-April, the FBI "missed an opportunity to catch its error" when it received word that the Spanish police laboratory had determined the print on the bag did not belong to Mayfield, Fine said.

Mayfield was taken into custody when the FBI feared the news media would publicly report on the investigation and Mayfield would flee or destroy evidence, Fine said.

Less than two weeks later, Spanish authorities told the FBI they had definitively identified an Algerian suspect as the owner of the fingerprint. On May 24, the FBI lab acknowledged its mistake.