Judge Emmet Sullivan on Monday threatened to sanction federal prosecutors in the trial of Sen. Ted Stevens (R-Alaska) after attorneys arranged for a key witness to return to Alaska despite outstanding subpoenas from Stevens’ defense team.

Stevens is charged with filing false financial statements over an eight-year period to conceal the receipt of more than $250,000 in gifts — primarily in renovations to his Girdwood, Alaska, home — from the now-defunct VECO oil services firm and its executives. He has pleaded not guilty.

Stevens’ attorneys filed a motion Sunday night alleging federal prosecutors withheld information about a key witness, Rocky Williams, a former VECO employee whom several witnesses in the case have identified as the day-to-day supervisor of the Girdwood renovations project.

Although federal prosecutors reportedly interviewed Williams in mid-September, the attorneys ultimately determined not to call Williams as a witness and arranged for his return to Alaska on Sept. 25, the same day of opening statements in the trial.

“It appeared that Williams may have been in Washington, D.C., for a rather significant period of time prior to the date of opening statement … the government made a unilateral decision to put him on a commercial flight and send him away from the court, knowing that he had also been subpoenaed by defense counsel,” a visibly agitated Sullivan said Monday. “Williams was informed, that: ‘When you arrive in Alaska, you might want to call the other side.’ … I’m concerned that a subpoenaed witness was … advised to leave the District of Columbia, and indeed assisted in leaving the District of Columbia by the government for reasons that have not been fully explored.”

Sullivan directed both sets of attorneys to file statements regarding the incident by Tuesday.

“I’m not suggesting at this point that there’s been misconduct on the part of government attorneys, but I want the parties to brief the issue,” Sullivan said. “If that’s the case, then I’m going to impose sanctions as appropriate.”

Sullivan did not specify what those sanctions could be.

Although Stevens’ attorneys had also sought to dismiss the trial or declare a mistrial, Sullivan rejected that motion, instead ruling that some witnesses could be called to testify a second time in court.