WASHINGTON — A lawyer Michael T. Flynn recently hired said on Monday that she would most likely need a security clearance to review classified materials that were separate from the documents that prosecutors for the special counsel, Robert S. Mueller III, had already handed over in the case.
The lawyer, Sidney Powell, made the unusual disclosure during a hearing in Federal District Court despite prosecutors’ insistence that they included no classified information in the evidence they shared with the defense. Her remarks heightened speculation that Ms. Powell — who has pushed conspiracy theories about the special counsel’s investigation and sells anti-Mueller T-shirts on her website — may be preparing to accuse the government of wrongdoing in Mr. Flynn’s case.
“There is other information,” she said, but she declined to elaborate.
One of the prosecutors, Brandon Van Grack, said he did not know what she was referring to. “There’s nothing that the government produced that’s classified,” Mr. Van Grack said.
Ms. Powell did not return a telephone message seeking further comment. Another lawyer working with her declined to comment. President Trump and his allies have long contended that Mr. Flynn and others were illegally targeted by the F.B.I. and intelligence community as part of a broad conspiracy to undermine the president.
Ms. Powell made the remarks at a status hearing, where a judge delayed sentencing for Mr. Flynn until after he testifies in July in an unrelated case. Mr. Flynn pleaded guilty in December 2017 to making false statements to F.B.I. agents about his contacts during the transition with the Russian ambassador.
Security clearances are not doled out easily. Typically, defense lawyers need a government agency to sponsor them and then the F.B.I. has to conduct a background check. The judge overseeing the case, Emmet G. Sullivan, said that a classified security officer would help Ms. Powell.
Mr. Flynn has not said why he changed lawyers, but Mr. Trump praised the move, leading some to believe that Mr. Flynn may pull out of his plea agreement or receive a pardon from the president. A former lawyer for Mr. Trump, John M. Dowd, broached the prospect of a pardon with a lawyer for Mr. Flynn in 2017. No evidence has emerged that the president asked his lawyer to convey such a message
Mr. Mueller’s team had recommended no prison time for Mr. Flynn, who was to have been sentenced in December. But at that hearing, Judge Sullivan, of the United States District Court for the District of Columbia, excoriated Mr. Flynn for claiming that the F.B.I. had set him up to make a false statement when he lied to agents about his contacts with the ambassador. The judge hinted that he may give Mr. Flynn a harsh sentence and allowed him to delay his sentencing so he could make a stronger case for how he had helped the government.
Mr. Flynn’s firing of his lawyers was revealed in a court filing on the same day that an audio recording that his previous lawyers gave to investigators was made public. On the recording, Mr. Dowd told one of Mr. Flynn’s lawyers shortly after he agreed to cooperate with prosecutors that the president would look favorably upon him if he shared information about the case.
The content and the tone of Mr. Dowd’s voice set off speculation that he was dangling a pardon for Mr. Flynn. Mr. Dowd has denied wrongdoing and criticized the Mueller inquiry as an effort to smear the president.
Mr. Trump’s lawyers said throughout the Mueller investigation that the president would wait until it concluded to determine whether to pardon anyone associated with it. Since the investigation ended in March, the president has praised Mr. Flynn and stopped short of dismissing the prospect of a pardon.
“He was a man who had an incredible record in the military, you see what happened to him,” Mr. Trump said in a phone interview on Fox News’s “Hannity.” He added, “You know what he has gone through.”
“I don’t want to talk about pardons now, but I can say it’s so sad on so many levels,” the president said.
As for Mr. Flynn’s new lawyer, Ms. Powell, she sells T-shirts that show caricatures of officials who have been involved in the investigation — like Mr. Mueller and the former F.B.I. director James B. Comey — above the hashtag #CreepsOnAMission.