The prosecutor who headed the Justice Department unit that bungled the corruption case against Sen. Ted Stevens is leaving the government.

In court papers filed Monday in a case in Virginia, the department says William Welch is departing for a job in the private sector.

Recently, Welch has overseen efforts to crack down on officials who leak government secrets. He stepped down as chief of the public integrity section in 2009 amid the controversy over the botched Stevens prosecution. A court-ordered investigation of that case concluded that prosecutors failed to turn over to Stevens' lawyers some information they had that was favorable to the defense.

Following Stevens' conviction in 2008, an FBI agent _ a government whistleblower _ alleged prosecutors had withheld evidence that undercut the testimony of the government's key witness against the senator. The judge dismissed the conviction at the request of Attorney General Eric Holder.

A month ago, a special counsel who looked into the Justice Department's mishandling of the Stevens prosecution found that Welch directly supervised the conduct of the case only when matters were brought to his attention after controversies arose.

The court-appointed special counsel, Henry Schuelke, said that to Welch's credit, on those occasions he directed that disclosure be made to Stevens' lawyers.

A separate investigation by the Justice Department's Office of Professional Responsibility concluded Welch did not commit professional misconduct or exercise poor judgment in the Stevens case. That conclusion was contained in a letter by OPR to Welch's lawyer, who included it in a response to the Schuelke report.

A jury convicted Stevens of seven felony counts of lying on Senate financial disclosure documents to hide hundreds of thousands of dollars in home renovations and gifts from wealthy friends, including a massage chair, a stained-glass window and an expensive sculpture. A few days later, Stevens lost re-election to the seat he'd held for 40 years, making him the longest-serving Republican in the Senate at the time. Stevens died in a plane crash on August 9, 2010.

More recently, Welch led the prosecution of Thomas Drake, a former senior National Security Agency official who faced 35 years in prison for disclosing government waste and mismanagement for a reporter. The case crumbled last year. A federal judge lambasted the government's handling of the case and sentenced Drake to community service and probation for one misdemeanor.

Welch also was overseeing the pending prosecution of former CIA officer Jeffrey Sterling, who is accused of disclosing information about a botched intelligence operation in Iran to Pulitzer-winning New York Times journalist and author James Risen. The Justice Department notified a federal appeals court in Richmond that Welch was withdrawing to take an undisclosed job in the private sector.