WASHINGTON — Attorney General Eric Holder announced today that he is shifting some office heads at the Justice Department, putting a career Washington prosecutor in charge of the internal ethics unit.

Holder announced today that Mary Patrice Brown will lead the Office of Professional Responsibility, which was established after Watergate but drew criticism from a federal judge this week.

The announcement came one day after a federal judge ordered a criminal investigation into whether Justice Department attorneys violated the law in the prosecution of former Alaska Sen. Ted Stevens. Justice officials say the department changes were not related to the case.

A jury convicted Stevens on corruption charges last fall, causing him to narrowly lose his Senate seat a few days later. But the conviction was thrown out Tuesday because of concerns about Justice’s mishandling of the case.

U.S. District Judge Emmet Sullivan expressed concern that the Justice review of the case was taking too long and was too important to be left to an internal review. He took the extraordinary step of naming a special prosecutor to determine whether prosecutors’ failure to turn evidence over to Stevens’ defense team violated the law.

Holder moved the current chief of the ethics unit, H. Marshall Jarrett, to lead the executive office of U.S. attorneys. Jarrett will replace Kenneth E. Melson, who will serve as acting chief of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The three appointments were first reported by The Washington Post.