The special counsel Robert Mueller's office said federal sentencing guidelines say Paul Manafort should get between 19.5 and 24.5 years in prison for the crimes he's been convicted of.

Earlier this week, a federal judge ruled that Manafort breached his plea deal with Mueller's office when he lied to prosecutors about several threads in the Russia probe, including about his interactions with the Russian intelligence operative Konstantin Kilimnik.

This month, one of Mueller's prosecutors revealed that they're focusing on discussions the two men had about a mysterious Russia-Ukraine "peace plan" — and the motive behind such discussions — from August 2016 continuing into 2018.

Legal experts were flummoxed by Manafort's decision to lie to prosecutors when cooperating would have gotten him a more lenient sentence.

One criminal defense attorney, who requested anonymity because they are actively involved in the Mueller probe, floated a theory: "Maybe Manafort was lying because telling the truth would reveal something more sinister."

The special counsel Robert Mueller's office said in a new court filing that federal sentencing guidelines say Paul Manafort, the former chairman of President Donald Trump's campaign, should get between 19.5 and 24.5 years in prison for the crimes he's been convicted of.

"In the end, Manafort acted for more than a decade as if he were above the law, and deprived the federal government and various financial institutions of millions of dollars," the sentencing memo reads. "The sentence here should reflect the seriousness of these crimes, and serve to both deter Manafort and others from engaging in such conduct."

Prosecutors added, however, that "the government does not take a position as to the specific sentence to be imposed here."

The filing came after US District Judge Amy Berman Jackson ruled Wednesday that Manafort lied to prosecutors in three out of five instances outlined by Mueller's office.

Jackson ruled that Manafort lied after striking a plea deal with Mueller's team last year, following his conviction on several counts of tax and bank fraud.

The judge voided Manafort's plea deal as a result, and the court released Mueller's office from any obligations it had under the original cooperation agreement.

The Wednesday ruling did not make a determination on whether Manafort "will receive credit for his acceptance of responsibility" in connection to federal sentencing guidelines, adding that the court would decide that when Manafort went to his final sentencing hearing.

"As an initial matter, the government agrees with the guidelines analysis in the Presentence Investigation Report (PSR) and its calculation of the defendant’s Total Offense Level as 38 with a corresponding range of imprisonment of 235 to 293 months, a fine range of $50,000 to $24,371,497.74, a term of supervised release of up to five years, restitution in the amount of $24,815,108.74, and forfeiture in the amount of $4,412,500," prosecutors wrote in their sentencing memo Friday.

The government "does not take a position as to the specific sentence to be imposed here," the memo also says.

Manafort's apparent decision to lie to prosecutors after agreeing to cooperate flummoxed legal scholars and Justice Department veterans.

One criminal defense attorney, who requested anonymity because they are actively involved in the Mueller probe, floated a possible theory. "Maybe Manafort was lying because telling the truth would reveal something more sinister," the attorney told INSIDER. "Who else would risk doing something this stupid without a guarantee of freedom?"

Read more: 'Like a guy shooting craps down to his last chip': Paul Manafort just made his riskiest gamble yet

Prosecutors zero in on Manafort's ties to Kilimnik

Robert Mueller. Chip Somodevilla/Getty Images

Jackson's ruling said that Manafort made false statements to prosecutors about:

A $125,000 payment made to a firm in 2017 related to a debt that Manafort had incurred.

His interactions with the former Russian intelligence operative Konstantin Kilimnik, and Kilimnik's role in the alleged conspiracy to obstruct justice by trying to influence the testimony of two witnesses in February.

Information that was "pertinent to another Department of Justice investigation."

Mueller's office also earlier revealed that Manafort shared confidential 2016 Trump campaign polling data with Kilimnik.

Manafort used Kilimnik as a conduit to the Russian oligarch Oleg Deripaska during the campaign, according to Mueller's office. According to reports, Manafort was deep in debt to several pro-Russian individuals and entities at the time, including Deripaska, who is a close ally of Russian President Vladimir Putin.

When Manafort took over as campaign chairman, he asked Kilimnik to update Deripaska on his elevated role on the Trump campaign. He also offered to give Deripaska "private briefings" about the operation.

The US intelligence community concluded in early 2017 that the Kremlin mounted an elaborate and multi-faceted campaign to interfere in the 2016 US election in order to elevate Trump to the presidency. Mueller's office is investigating whether the Trump campaign coordinated with Russia during the 2016 campaign.

Mueller prosecutor: ' This goes, I think, very much to the heart of what the special counsel's office is investigating'

Russian tycoon Oleg Deripaska. REUTERS/Sergei Karpukhin

Mueller's team is closely scrutinizing Manafort's relationship with Kilimnik. Prosecutors are known to be eyeing, in particular, a meeting between the two men that took place on August 2, 2016 and the events surrounding it.

Three days before the meeting, Kilimnik and Manafort emailed back and forth about relaying "several important messages" from "the guy who gave [Manafort his] biggest black caviar jar several years ago," allegedly in reference to Deripaska and his loans to Manafort.

"We spent about 5 hours talking about his story, and I have several important messages from him to you," Kilimnik wrote, adding, "I need about two hours because it is a long caviar story to tell."

Manafort said he and Kilimnik discussed the Trump campaign and the recent hack of the Democratic National Committee during the meeting on August 2, 2016. Kilimnik, meanwhile, said they did not discuss the campaign but talked about "current news" and "unpaid bills."

Shortly after the August 2 meeting, a jet linked to Deripaska landed in Newark, New Jersey, and was in the US for less than 24 hours.

Read more: Mueller dropped an intriguing hint about where the Russia probe is headed in a new court filing

Prosecutors are also looking into discussions Manafort and Kilimnik had around the same time about a plan to end the conflict in Ukraine after Russia annexed the territory of Crimea in 2014, according to comments one of Mueller's prosecutors made at a court hearing this month about Manafort's lies.

The prosecutor, Andrew Weissman, said at the hearing that Manafort and Kilimnik communicated extensively about the so-called Ukraine peace plan beginning in early August 2016 and continuing into 2018, months after Manafort was first indicted by the special counsel.

When the judge pressed Weissman on why Manafort's lies mattered, Weissman responded, "This goes to the larger view of what we think is going on, and what we think is the motive here."

"This goes, I think, very much to the heart of what the special counsel's office is investigating," he added.