A U.S. federal judge dropped a corruption conviction of former Alaska Senator Ted Stevens Tuesday and ordered a probe into the conduct of prosecutors who handled the case.

District Judge Emmet Sullivan accused prosecutors of the most serious misconduct he has seen during his 25 years on the bench. The federal judge in Washington appointed a special attorney to investigate the prosecutors for possible criminal contempt charges.

US Judge Drops Guilty Verdict Against Former Senator

The 85-year-old former lawmaker was convicted in October on seven counts of lying about gifts and home renovations he received. Shortly afterwards, Stevens, who had been the longest serving Republican in the U.S. Senate, narrowly lost his re-election bid.

US Judge Drops Guilty Verdict Against Former Senator

The Justice Department moved last week to drop the conviction and indictment against Stevens, saying prosecutors had mishandled the case by withholding information from the defense.

US Judge Drops Guilty Verdict Against Former Senator

Stevens said Tuesday that the actions of the prosecution team nearly destroyed his faith in the U.S. judicial system.