The former deputy attorney general Sally Q. Yates on Wednesday adamantly defended the Justice Department’s investigation of Michael T. Flynn, clashing with Senate Republicans who accused her of being part of a politically motivated ploy by the Obama administration to frame President Trump’s former national security adviser.
In testimony before the Senate Judiciary Committee, Ms. Yates described how top White House officials became deeply alarmed when they learned in the waning days of President Barack Obama’s tenure that the top national security adviser to the incoming president was conducting secretive talks with the Russian ambassador. They worried that Mr. Flynn’s purpose was to undercut new American sanctions against Moscow, and that he was apparently withholding those discussions from the incoming vice president.
The F.B.I. eventually responded by dispatching agents to interview Mr. Flynn, who later pleaded guilty to lying to them about his conversations with the ambassador. Though Ms. Yates did not sign off on the interview and disagreed with the process, she argued on Wednesday that it had been justified as a means to better understand what law enforcement officials viewed as a possible counterintelligence threat, especially in the context of an open investigation into possible links between the Trump campaign and Russia.
“General Flynn had essentially neutered the U.S. government’s message of deterrence,” she said. “Far from rebuking the Russians for their attack on our country, General Flynn was conciliatory.”
Her testimony was sharply at odds with the message of Republican lawmakers who control the panel and convened the hearing as part of an inquiry to discredit the broader Trump-Russia investigation, which many of them view as corrupt. Allies of Mr. Trump hold up the case of Mr. Flynn as evidence of investigative abuse, and Attorney General William P. Barr moved this spring to drop the prosecution of the case altogether.
Three and a half years after most of the events in question took place, the hearing drew out few, if any, new facts. Rather, it was another chance for lawmakers in both parties to fight over what those facts meant.
In the hearing room, Senator Lindsey Graham, Republican of South Carolina and the committee’s chairman, insisted that Mr. Flynn had “every right” to talk to the Russian ambassador as he did, and suggested that the previous administration was trying to use an obscure 1799 statute, the Logan Act, to punish him for a policy disagreement.
“What we are doing here is criminalizing policy differences,” he fumed, specifically calling out Mr. Obama and Joseph R. Biden Jr., the former vice president and presumptive Democratic presidential nominee. “That’s why Flynn got prosecuted, because they hated his guts.”
Ms. Yates repeatedly rejected Republicans’ sinister characterization of events.
“The whole prism you have here that this is all about the Logan Act is just not how we ran things,” Ms. Yates told Mr. Graham.
She said that Mr. Obama and Mr. Biden were purely interested in ensuring that it was safe to share sensitive government secrets with Mr. Flynn after public comments about his talks with the Russian ambassador contradicted intelligence intercepts of their conversations.
They “did not in any way attempt to direct or influence any kind of investigation,” she said. “Something like that would have set off alarms for me.”
As she has before, Ms. Yates said that she had been deeply frustrated with how James B. Comey, the former F.B.I. director, handled the investigation into Mr. Flynn. She agreed with Mr. Graham’s suggestion that Mr. Comey went “rogue” in circumventing her to set up the interview with Mr. Flynn in late January without telling Trump administration officials. But she defended the bureau’s actions.
And she said Mr. Barr’s decision to drop the case after Mr. Flynn had admitted guilt was “highly irregular.”
In an extraordinary intervention this spring, Mr. Barr informed a federal court where Mr. Flynn had twice pleaded guilty that prosecutors mishandled the case, that the F.B.I. should never have interviewed Mr. Flynn in the first place and could not prove beyond a reasonable doubt that his false statements were relevant to the Russia investigation, as prosecutors had originally claimed. The department cited statements by Ms. Yates in justifying its decision.
On Wednesday though, she made it clear that she saw the false statements as extremely relevant and easily proved by prosecutors.
Under questioning by Senator Patrick J. Leahy, Democrat of Vermont, Ms. Yates also rejected Republican suggestions — based in part on open-ended notes taken at the time by a top Justice Department official — that the F.B.I. had been trying to goad Mr. Flynn into lying. She pointed out that agents had repeatedly tried to jog Mr. Flynn’s memory after he failed to mention the sanctions discussion.
“If you are trying to set somebody up to lie — which I don’t really know how you set somebody up to lie — you don’t generally help them out like that,” she said.
A divided three-judge panel of the Federal Appeals Court in Washington had moved to side with the government and Mr. Flynn and dismiss the case in June. But after a vote of its members, the entire court announced last week that it would erase that decision and review the case anew, prolonging Mr. Flynn’s legal limbo.
Ms. Yates also testified that knowing what she knew now about errors and omissions in a secret court application to wiretap Carter Page, a former Trump campaign adviser, she would not have signed off on the paperwork.
The department’s inspector general, Michael E. Horowitz, uncovered serious errors and omissions in the applications, including questioning the use of information from a salacious dossier compiled by Christopher Steele, a former British intelligence agent whose research was funded by Democrats, that was unverified and later called into question.
“I certainly regret that the Department of Justice submitted with the F.B.I. FISA applications that were inaccurate,” Ms. Yates said under sharp questioning by Republicans, referring to the Foreign Intelligence Surveillance Act. “I think that is antithetical to our responsibility to the FISA court. I think it is also inconsistent with what my experience with the F.B.I. had been.”
Ms. Yates’s testimony echoed that of Rod J. Rosenstein, another former deputy attorney general under Mr. Trump, who told the committee that he, too, would not have signed a separate application to renew a court wiretap order targeting Mr. Page if he had known that it contained errors and omissions.
Some Republican senators, piqued by those responses, lit into Ms. Yates.
“What responsibility do you bear for the deliberate and systematic misleading of a federal court?” Senator Josh Hawley, Republican of Missouri, asked her.
Senator John Kennedy, Republican of Louisiana, posited that she despised Mr. Trump.
“I think you and your colleagues have tarnished the reputation of the F.B.I.,” he said.
As the hearing got underway, Mr. Trump slammed Ms. Yates on Twitter with dubious claims. He said she had “zero credibility,” accused her of aiding “the greatest political crime of the Century” and insinuated that she might have leaked details of Mr. Flynn’s conversations with the ambassador to the news media at the time — something she has already denied under oath.
“ObamaBiden knew EVERYTHING!” he wrote.
Mr. Graham disagreed during the hearing with Mr. Trump and some of his own members, repeatedly telling Ms. Yates that he believed she had acted properly by seeking to inform the White House about Mr. Flynn’s apparent deception.