Special Counsel Robert Mueller recommended that a federal judge to sentence George Papadopoulos, a former campaign aide of US President Donald Trump, to up to six months in prison for lying to investigators in relation to the ongoing Russian Federation meddling probe.
Papadopoulos pleaded guilty in October 2017 of one count of lying to FBI agents working for Mueller's investigation into Russian meddling in the 2016 election.
The Mueller court documents said Mr Papadopoulos caused irreparable damage to the Russian Federation investigation because he lied repeatedly to agents during a January 2017 interview.
"The government does not take a position with respect to a particular sentence to be imposed, but respectfully submits that a sentence of incarceration within the applicable guidelines range of zero to six months imprisonment is appropriate and warranted", Mr Mueller's memorandum to the judge in the case says.
Prosecutors also detail a series of hard interviews with Papadopoulos after he was arrested in July 2017, saying he didn't provide "substantial assistance" to the investigation.
Friday's 10-page filing provided fresh details of how Papadopoulos' lies impeded the Federal Bureau of Investigation, according to prosecutors, who went on to say his lack of cooperation justified a prison term.
Mueller also said Papadopoulos avoided until the last moment telling prosecutors about a cell phone he used in London that had "substantial communications" on it between he and the professor who claimed to know about Russian information on Clinton.
The Australians said Papadopoulos told one of their diplomats that he had been informed by Mifsud that the Russians had damaging material about Democratic candidate Hillary Clinton. The only defendant to be sentenced is lawyer Alex van der Zwaan, who pleaded guilty to making false statements about his conversations with a former Trump campaign official.
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Another question asked for a definition of "shelf company;" the typical term is "shell company", according to the New York Times . Manafort lied to keep more money when he had it, and he lied to get more money when he didn't", prosecutor Greg Andres said.
It also reveals Federal Bureau of Investigation agents first interviewed Papadopoulos at the Chicago field office on January 27, 2017.
"The defendant's false statements were meant to harm the investigation, and did so", the government's filing says. It was in that conversation prosecutors said "he proceeded to answer questions, and to lie, for more than two hours".
It says he was warned about the seriousness of the investigation and that he might have important information to provide.
Papadopoulos' attorneys, Thomas Breen and Robert Stanley, have until August 31 to file a sentencing recommendation of their own.
Van der Zwaan was sentenced in April.
The filing suggests Papadopoulos hampered the FBI's ability to figure that out.
Prosecutors also note investigators missed an opportunity to interview others about the professor's comments or anyone else at that time who might have known about Russian efforts to obtain derogatory information on Clinton during the campaign.
Thirty-two people have been charged by Mueller's office since it took over the investigation in May 2017.