Washington ? The conviction of an inmate who spent 10 years in prison has been overturned because an FBI scientific expert gave inaccurate testimony and withheld evidence — one of the first reversals arising from an investigation of the FBI lab.

The FBI agent, Michael Malone, was transferred from the lab after the problems were discovered but continued to work for the bureau until his retirement in December 1999.

The government disclosed to defense lawyers in 2001 that Malone had engaged in misconduct as a witness in the case of Anthony E. Bragdon, officials said.

Bragdon, now 31, was convicted by a jury in 1992 in District of Columbia Superior Court of assault with intent to rape. By the time the government divulged Malone’s problems to Bragdon’s lawyers and the appeals process started, the inmate already had served 10 years in prison.

The same court recently overturned his conviction, and federal prosecutors told the judge they wouldn’t retry him.

Bragdon’s freedom is an outgrowth of a sweeping investigation in the 1990s prompted by a whistleblower’s allegations that his FBI lab colleagues had performed shoddy work and shaded the truth to help prosecutors.

The internal investigation concluded in 1997 that there were problems with the work and testimonies of several FBI scientists, including Malone, and the FBI lab made changes to ensure the quality of its future work.

The Associated Press reported in March that a review had identified about 3,000 cases that could have been affected but only 150 defendants had been notified of problems.