WASHINGTON — The Justice Department dropped its criminal case on Thursday against Michael T. Flynn, President Trump’s first national security adviser, who had previously pleaded guilty to lying to F.B.I. agents about his conversations with a Russian diplomat.
The extraordinary move comes amid a sustained attack by Mr. Flynn’s lawyers on prosecutors and the F.B.I., accusing them of egregious conduct. In recent days, Mr. Flynn’s lawyers said the Justice Department had uncovered new documents that pointed to misconduct, particularly in investigators’ interview of Mr. Flynn in January 2017 as part of its inquiry into whether Trump advisers conspired with Russia’s election interference.
Law enforcement officials cited that interview in moving to drop the charges, saying in a court filing that the some of newfound documents showed that the questioning “was untethered to, and unjustified by, the F.B.I.’s counterintelligence investigation into Mr. Flynn.” Prosecutors said that the case did not meet the legal standard that Mr. Flynn’s lies be “materially” relevant to the matter under investigation.
“The government is not persuaded that the Jan. 24, 2017, interview was conducted with a legitimate investigative basis and therefore does not believe Mr. Flynn’s statements were material even if untrue,” the United States attorney in Washington, Timothy L. Shea, said in a motion to dismiss the charges.
In a possible sign of disagreement, Brandon L. Van Grack, the Justice Department lawyer who led the prosecution of Mr. Flynn, abruptly withdrew from the case on Thursday. Mr. Flynn’s lawyers have repeatedly attacked Mr. Van Grack by name in court filings, citing his “incredible malfeasance.” Prosecutors in Mr. Shea’s office were stunned by the decision to drop the case, according to a person who spoke to several lawyers in the office.
The move also appeared to be the latest example of Attorney General William P. Barr’s efforts to chisel away at the results of the Russia investigation. The documents that Mr. Flynn’s lawyers have cited were turned over as a result of a review by an outside prosecutor whom Mr. Barr assigned to review the Justice Department’s case. Mr. Barr has cast doubt not only on some of the prosecutions in the broader Russia investigation but also on the premise itself, assigning another independent prosecutor to scrutinize the inquiry’s origins.
Responding to the news, Mr. Trump told reporters that Mr. Flynn was “an innocent man,” and said he now views him as an “even greater warrior.” Sidney Powell, Mr. Flynn’s lawyer, did not respond to a request for comment.
A former senior F.B.I. official involved in investigating Mr. Flynn defended the bureau’s actions and accused officials of politicizing law enforcement.
“The department’s position that the F.B.I. had no reason to interview Mr. Flynn pursuant to its counterintelligence investigation is patently false, and ignores the considerable national security risk his contacts raised,” the official, Andrew G. McCabe, said in a statement.
“Today’s move by the Justice Department has nothing to do with the facts or the law — it is pure politics designed to please the president,” added Mr. McCabe, a frequent target of Mr. Trump’s who was fired as deputy director of the F.B.I. over failing to be forthcoming in an internal inquiry. He has said he was dismissed to undermine the Russia investigation in which he was a witness.
Mr. Flynn first pleaded guilty in late 2017 to lying to investigators and cooperated extensively before moving to withdraw his plea and fight the case in court. He had also entered a guilty plea a second time in 2018 at an aborted sentencing hearing.
It is now up to the federal judge in Washington overseeing the case, Emmet G. Sullivan, to decide whether to dismiss the case and close off the possibility that Mr. Flynn could be tried again for the same crime. If the judge wants, he could ask for written submissions and hold a hearing on that topic.
Judge Sullivan, who accepted Mr. Flynn’s original guilty plea, could also weigh in on whether he believes any of the new materials that the government has produced to Mr. Flynn’s lawyers represent any violation on the part of the Justice Department or its lawyers who worked on the case.
The White House was prepared for the possibility of Mr. Trump pardoning Mr. Flynn last week, according to two people familiar with the discussions. But some advisers urged him to hold off and let the case play out, either with the Justice Department or with the judge in the case, according to the people familiar with the discussions.
So Mr. Trump agreed, and he held off. If he was briefed by Mr. Barr long before the decision, he did not let on to advisers, according to those familiar with the discussions.
Mr. Flynn’s case grew out of an investigation by law enforcement officials who had reason to suspect that he constituted a national security threat. They learned that he had lied in January 2017 to other White House officials about conversations during the presidential transition with the Russian ambassador to the United States, and they warned the White House that Russia could have blackmailed Mr. Flynn, then the Trump administration’s highest-ranking national security official.
After more than a year of cooperating with investigators, Mr. Flynn adopted a more combative stance last year when he hired new lawyers who have accused Mr. Van Grack and other prosecutors in a blizzard of court filings of “bad faith,” pressuring their client to cooperate and withholding exculpatory evidence.
One of the lawyers, Sidney Powell, has been critical of the Russia investigation during appearances on Fox News and has sold T-shirts on her website that mock the investigators. The president has praised Mr. Flynn’s decision to hire her.
But Judge Sullivan forcefully rejected most of the defense’s claims in a 92-page ruling in December.
Mr. Flynn, a decorated lieutenant general and former head of the Defense Intelligence Agency, was an early supporter of Mr. Trump’s campaign, joining the crowd in a “lock her up” chant about Hillary Clinton at the Republican National Convention in 2016.
Mr. Flynn pleaded guilty in December 2017 to lying to the F.B.I. about his conversations during the presidential transition with the Russian ambassador to the United States at the time, Sergey I. Kislyak.
The F.B.I. had interviewed Mr. Flynn four days after Mr. Trump’s inauguration. Less than a month later, Mr. Flynn was forced to resign as national security adviser. According to the White House at the time, the reason Mr. Flynn was forced to resign was because he was not forthcoming with Vice President Mike Pence about his conversations with Mr. Kislyak.
Mr. Flynn eventually admitted that those discussions were part of a coordinated effort by the president’s aides to make foreign policy before they were in power, which undermined the policy of President Barack Obama.
Mr. Flynn also lied in federal filings about his lobbying work for the Turkish government, court papers show. Two of his former business associates were charged with conspiring to violate federal lobbying rules in cases related to the special counsel inquiry.
Mr. Trump raised concerns about the F.B.I.’s scrutiny of Mr. Flynn during the early days of his presidency, asking the F.B.I. director at the time, James B. Comey, to end any investigation into Mr. Flynn. Details about the president’s request became public a few months later after Mr. Trump fired Mr. Comey and helped prompt Mr. Mueller’s appointment as special counsel.
After firing Mr. Flynn, the president thought he had put an end to the Russia inquiry that had been dogging him for months.
“Flynn met with the Russians. That was the problem. I fired Flynn. It’s over,” Mr. Trump said, according to a book published by former Gov. Chris Christie of New Jersey, an ally of the president’s.
The special counsel’s prosecutors considered Mr. Flynn a key early cooperator as “one of the few people with long-term and firsthand insight” into their inquiry into whether any Trump associates criminally conspired with Russia’s 2016 election interference.
Morale in the U.S. attorney’s office in Washington, which handled the Flynn investigation, has been low since Mr. Barr directed prosecutors in February to lower their sentencing recommendation for Mr. Trump’s longtime friend Roger J. Stone Jr. for crimes he committed in a bid to protect the president. Though Mr. Trump had publicly complained about the prosecutors’ sentencing recommendation, the department has said that Mr. Barr made that decision regardless of that request.
Michael Crowley contributed reporting from Washington, and Maggie Haberman from New York.