Prosecutors on Tuesday filed a sentencing memorandum in the case of Flynn, who pleaded guilty a year ago to lying to the Federal Bureau of Investigation regarding conversations about sanctions with the Russian ambassador.
Mueller's office says Flynn assisted them 'on a range of issues, including interactions between individuals in the Presidential Transition Team and Russian Federation'.
Flynn was forced to resign his post on February 13, 2017, after news reports revealed that Obama administration officials had warned the Trump White House about Flynn's false statements. Stone told ABC News on Sunday he would not testify against Trump and has not discussed a pardon with the president.
Friends and relatives have said Flynn, who at 2016 campaign rallies led chants of "Lock her up!" about Democratic nominee Hillary Clinton, is eager to face the judge and accept his fate following his dramatic guilty plea nearly exactly one year ago. Flynn was under investigation by the Justice Department for that work when he became national security adviser. Flynn later pleaded guilty to perjury and is cooperating with Mueller. Also, Paul Manafort, a convicted felon who just blew up his cooperation deal with Mueller, is "a courageous man" who "refused to 'break'" and therefore has earned "such respect" from Trump.
Michael Cohen US President Donald Trump’s former attorney and fixer
The filing details the series of false statements Flynn made to the Federal Bureau of Investigation and the Justice Department.
Flynn's case has been a contrast to those of other Trump associates, who have criticized the Russian Federation probe. Manafort, Trump's former campaign chairman, was found guilty on eight counts of financial crimes.
The government notes that Flynn "falsely stated that he did not ask the Russian ambassador to refrain from escalating the situation in response to the sanctions" and further, "falsely disclaimed any memory" of his subsequent conversation with Kislyak, in which Kislak told Flynn that Russia had complied with Flynn's request.
He was forced out over revelations that he had discussed lifting U.S. sanctions on Russia with the Russian ambassador to Washington before Mr Trump took office, and that he lied to the United States vice-president about that conversation. Flynn was in the White House for less than a month before he was sacked for lying to Vice President Mike Pence about his contacts with Russian officials.
The national security experts at Lawfare wrote, moreover, that the public might also learn more "in the context of that briefing about the relationship Manafort appears to have maintained, through counsel, with the White House after his plea and cooperation agreement".