The sentencing memo is also expected to shed light on how the special counsel has evaluated Flynn's cooperation in its ongoing probe of Russia interference in the 2016 U.S. presidential election. Mueller is also looking into potential coordination between the Trump campaign and Russia, as well as an obstruction-of-justice probe.
Flynn pleaded guilty last December to lying to the FBI about his contacts with a Russian official. Mueller could potentially ask a federal judge to reduce Flynn's sentence because he agreed to cooperate with the special counsel as part of his plea agreement.
Flynn served briefly as President Donald Trump's first national security advisor. He resigned in February 2017, after Vice President Mike Pence said Flynn lied to him about his conversations with Russian Ambassador Sergey Kislyak during the presidential transition period. The conversations revolved around sanctions that had been imposed by President Barack Obama's administration in retaliation for Russian interference in the U.S. presidential election.
Flynn's sentencing, and the documents to be filed from both parties that anticipate it, have been scheduled since September. After the special counsel submits its sentencing memo, Flynn will have a week to file his own version, followed by a reply from the government three days later on Dec. 14. The sentencing hearing itself is scheduled for the morning of Tuesday, Dec. 18, before Judge Emmet Sullivan in U.S. District Court in Washington, D.C.
Flynn was a fiery advocate for Trump on the campaign trail. He famously led a "lock her up" chant at the Republican National Convention, referring to Trump's opponent in the 2016 election, former Secretary of State Hillary Clinton. Trump and his surrogates often accused Clinton of breaking the law through her use of a private email server.
In 2018, Flynn mostly stayed out of the spotlight as other characters in the Russia probe took center stage.
On Thursday, Trump's former personal attorney Michael Cohen pleaded guilty to lying to Congress about plans for a Trump Tower development in Moscow.
In lower Manhattan federal court, Cohen admitted lying to the Senate Intelligence Committee when he said that the Moscow proposal "ended in January 2016 and was not discussed extensively with others" in the Trump Organization.
The project was still being discussed by Cohen and other Trump Organization figures as late as June 2016, according to documents filed by the special counsel.
Cohen has been interviewed at least seven times by Mueller's team, a time investment reportedly totaling about 70 hours. He and Flynn both pleaded guilty to a charge carrying a maximum sentence of five years in prison, a fine of up to $250,000 and three years of supervised release, according to their plea agreements. But their sentences are likely to be much smaller: Both of the deals provide an estimated sentencing range of between zero and six months in jail.
There is no indication that Flynn has broken the terms of his plea deal. Trump's former campaign chairman Paul Manafort, however, was accused of lying about a "variety of subject matters" after he had already struck a plea agreement, the special counsel told a federal judge on Nov. 26.
Manafort was convicted on eight criminal counts in Virginia federal court in August, and pleaded guilty a month later on the eve of a second trial on charges brought by Mueller in D.C. federal court. The charges related to his work for a pro-Russia political party in Ukraine, which occurred before he joined Trump's campaign in 2016.
Manafort "does not agree with the government's characterization or that he has breached the agreement," his lawyers said in a court filing. The special counsel and Manafort's attorneys both asked the judge to sentence the former Trump campaign chairman.