WASHINGTON -- The lead lawyer who oversaw the Alaska political corruption prosecutions, including the botched cases against former U.S. Sen. Ted Stevens and two former state legislators, will step down from his role as the head of the Justice Department's Public Integrity Section, the department said Wednesday.

William Welch II will remain with the Justice Department, but will be returning to a post in Massachusetts, said his attorney, William Taylor.

"While the ultimate result in the Stevens case has been highly disappointing professionally and personally, Bill knows that his management decisions, where permitted, comported with his own and the Department's highest ethical standards," Taylor said.

Welch, along with his former principal deputy and the four government lawyers involved day-to-day in the Alaska cases, remains under investigation for the flawed Stevens prosecution. The former Republican senator's indictment was part of a sweeping investigation into corruption in Alaska politics that began unraveling when defense attorneys questioned the way prosecutors and the FBI handled witnesses and evidence in Stevens' case and others.

In two related cases, two former state lawmakers, Pete Kott and Vic Kohring, were freed from prison in June when the government acknowledged they may not have gotten fair trials because favorable evidence was withheld from them. A judge is expected to rule later this year or early next on whether to dismiss charges or order new trials.

In Stevens' case, the Justice Department acknowledged it had failed to share with the former senators' lawyers notes from an interview with the prosecution's key witness. Those notes contradicted the witness's trial testimony and could have been favorable to Stevens at trial.

The Justice Department's Office of Professional Responsibility is pursuing its own internal investigation into what happened with Stevens' case, and the U.S. District judge who oversaw Stevens' trial last October, Emmet Sullivan, appointed a special prosecutor to investigate irregularities in the prosecution.