WASHINGTON — The federal judge overseeing the criminal case of President Trump’s former national security adviser Michael T. Flynn appointed a hard-charging former prosecutor and judge on Wednesday to argue against the Justice Department in its effort to drop the case and to investigate whether Mr. Flynn committed perjury, an extraordinary move in a case with acute political overtones.
Judge Emmet G. Sullivan of the United States District Court for the District of Columbia said in a brief order that he had appointed John Gleeson, a retired judge, “to present arguments in opposition to” the department’s request to withdraw the charge against Mr. Flynn, who had pleaded guilty to lying to investigators as part of a larger inquiry into Russia’s interference in the 2016 election before fighting the charge.
Judge Sullivan also asked Judge Gleeson to address whether the court should explore the possibility that Mr. Flynn opened himself up to perjury charges by pleading guilty under oath. Mr. Flynn entered guilty pleas twice in front of two judges.
The judge’s order was an astonishing move in the latest high-profile criminal case to prompt accusations from current and former law enforcement officials that Attorney General William P. Barr has politicized the Justice Department to protect allies of President Trump.
The Justice Department declined to comment. Judge Gleeson did not immediately respond to a request for comment.
Judge Sullivan had said a night earlier that he would consider briefs from outsiders known as amicus curiae, or “friend of the court,” who opposed the government’s request to dismiss the case against Mr. Flynn.
After a long campaign by Mr. Trump and his supporters, the department abruptly moved to the drop the charge against Mr. Flynn last week, saying that the lies that he had admitted to were immaterial to the matter under investigation and that agents’ questioning of him was unjustified.
While judges do sometimes appoint such third parties to represent an interest they feel is not being heard in the case, the move by Judge Sullivan is highly unusual, said Samuel Buell, a former federal prosecutor who now teaches criminal law at Duke University: He is essentially bringing in an outsider to represent the point of view of the original prosecutors in the case, who believed Mr. Flynn had committed a crime before Mr. Barr intervened and essentially replaced them with a prosecutor willing to say he had not.
“This is extraordinary for the judge to appoint somebody to argue against a prosecutors’ motion to dismiss a criminal case,” Mr. Buell said. “But it’s extraordinary for a prosecutor to move to dismiss this sort of criminal case.
“What the Justice Department did in the first case is, as far as any of us can figure out, unprecedented,” he added. “So the fact that this is pretty unprecedented too is not that surprising.”
It was not immediately clear what Judge Sullivan was focused on with his request for input on whether to essentially accuse Mr. Flynn of criminal perjury.
Mr. Buell said he doubted it would qualify as perjury for Mr. Flynn to embrace the Justice Department’s claim that he committed no crime because his admitted lies were purportedly immaterial to a proper investigation — whether or not that legal theory is true. But, Mr. Buell said, there could be a legitimate issue if Mr. Flynn were to claim that he did not lie after all — a notion the Justice Department’s filing also hinted at — despite previously telling judges that he had.
Mr. Flynn’s lawyers objected to Judge Sullivan’s order on Tuesday suggesting he would accept input from third parties and said that outside opinions were best left to Op-Ed sections. “This court is not a forum for their alleged special interest,” Mr. Flynn’s lawyers wrote in court papers.
Judge Gleeson, who served on the federal bench in Brooklyn and had run the criminal division in the federal prosecutor’s office there, has already made plain his skepticism of the motion to dismiss the Flynn case. He co-wrote an Op-Ed article this week in The Washington Post encouraging Judge Sullivan to scrutinize the motion.
“Prosecutors deserve a ‘presumption of regularity’ — the benefit of the doubt that they are acting honestly and following the rules,” he wrote along with two other former federal law enforcement officials in New York. “But when the facts suggest they have abused their power, that presumption fades.”
The department had made conflicting statements to the court, they wrote, saying that Judge Sullivan had the “authority, the tools and the obligation” to decide whether the department’s motion to withdraw was credible.
“There has been nothing regular about the department’s effort to dismiss the Flynn case,” they wrote. “The record reeks of improper political influence.”
The son of Irish immigrants, Judge Gleeson has said in interviewsthat he took a job as a prosecutor in Brooklyn after he was rejected from a post in the Manhattan federal prosecutor’s office, then run by Rudolph W. Giuliani.
As a prosecutor in Brooklyn, Judge Gleeson rose to legal stardom when he successfully prosecuted the notorious mobster John Gotti.