WASHINGTON -- Michael Flynn, who resigned as President Donald Trump's national security adviser just 24 days into his administration, has pleaded guilty to making false statements to the FBI, a federal crime.
The charge, which was unsealed on December 1, marks a major development in U.S. Special Counsel Robert Mueller's criminal investigation focusing on ties between Trump's 2016 presidential campaign and Russia.
The filing in U.S. federal court in Washington, D.C., dated November 30 said Flynn "willfully and knowingly" lied when he told the FBI he had not discussed U.S. sanctions imposed against Russia with Sergei Kislyak, then the Russian ambassador to the United States.
The document said the conversation happened during the transition period between the November 8, 2016, presidential election and Trump's inauguration on January 20, 2017.
Flynn, a retired U.S. Army lieutenant general who formerly served as a top intelligence official in President Barack Obama’s administration, did not respond to reporters' questions as he arrived at federal court in Washington.
His lawyers issued a statement from Flynn saying: "I recognize that the actions I acknowledged in court today were wrong, and, through my faith in God, I am working to set things right. My guilty plea and agreement to cooperate with the special counsel's office reflect a decision I made in the best interests of my family and our country."
Flynn faces up to five years in prison for the charge of lying to the FBI, but his sentencing could also depend on the extent of his cooperation with investigators.
Trump's lawyer, Ty Cobb, released a statement saying Flynn's guilty plea does not implicate anyone other than Flynn.
"The false statements involved [in the indictment] mirror the false statements to White House officials which resulted in [Flynn's] resignation in February," Cobb's statement said.
Neither Trump nor the White House made any statements in the hours after Flynn’s court appearance. A scheduled White House photo-op with Trump and the visiting Libyan prime minister was canceled. A White House Christmas party for the media, set for the afternoon on December 1, remained on the schedule.
Norm Eisen, who was a top ethics lawyer in Obama's administration, said the charge is relatively light, which could indicate Flynn has offered substantial cooperation to investigators.
"In practice, that means he will be cooperating against someone more important than he is; prosecutors don't in practice consider a defendant implicating peers or subordinates alone sufficient," he told RFE/RL in an e-mail.
Because Flynn was so high up in the campaign and the White House, he must have proffered information that can be used to make the case against others, he said.
Eisen said that might include Trump's son-in-law, Jared Kushner, Trump's son Donald Jr., or someone else of similar seniority -- perhaps even Trump himself.
Flynn resigned as Trump's national security adviser in February after it was revealed he misled Vice President Mike Pence about his contacts with Kislyak.
Mueller is leading a Justice Department investigation into contacts between Trump's election campaign and other Trump associates and Russian government agents.
Mueller took over the probe after Trump on May 9 abruptly fired FBI Director James Comey, whose investigators had begun their probe into possible collusion with Russia in July 2016.
Comey’s firing came about three months after he met with Trump at the White House. According to news reports, during that meeting, which occurred the day after Flynn’s resignation, Trump asked Comey to end the agency's investigation into Flynn.
The day after Comey’s firing, meanwhile, Trump met with Kislyak and Russian Foreign Minister Sergei Lavrov at the White House and reportedly told them he had fired Comey because of the Russia investigation.
If Mueller’s team were to determine that Trump fired Comey to block the criminal investigation, that could be considered obstruction of justice.
Flynn is the fourth person to be criminally charged in connection with the investigation. Former Trump campaign Chairman Paul Manafort and his business associate Rick Gates were indicted in October on charges that included conspiracy and lying to federal agents. Former foreign policy adviser George Papadopoulos, meanwhile, has pleaded guilty to lying to FBI agents and was cooperating with Mueller’s investigators.
In January, U.S. intelligence agencies issued a finding that the Russian government had conducted a concerted campaign to influence the 2016 election in favor of Trump.
ABC News reported that Flynn had indicated he was prepared to testify against Trump and other administration officials.
Michael Glennon, who served in the U.S. Senate Office of the Legislative Counsel during the Watergate crisis, said there were clear parallels to when President Richard Nixon’s White House counsel, John Dean, testified to a Senate committee and implicated administration officials in the Watergate burglary.
The events that followed resulted in Nixon resigning as congressional lawmakers drew up articles of impeachment.
“John Dean broke the dam and the question is whether Mike Flynn’s testimony is the dam breaker. That remains to be seen, but I would not be sitting pretty if I were in the Oval Office,” he told RFE/RL.
“Merely meeting with representatives of the Russian government or encouraging subordinates to meet with members of the Russian government does not, in and of itself, constitute obstruction of justice,” said Glennon, now a professor at the Fletcher School of Law and Diplomacy at Tufts University.
"Now, if lying to the FBI is part of a larger scheme aimed at preventing the law enforcement authorities to learn about illegal activities, that’s a different question," he said.