Rick Gates, a key witness in special counsel Robert Mueller's investigation, was sentenced Tuesday to 45 days in jail, which he can serve on weekends, and three years of probation.

Judge Amy Berman Jackson said she'd watched Gates testify twice and found him "extremely candid."

"He didn't appear to embroider the evidence to advance the government's case," Jackson said. "And he didn't come across as some bought and paid-for puppet."

The business associate of former Trump campaign manager Paul Manafort and a Republican operative found himself at the center of Mueller’s investigation into the Trump campaign and Russia. Gates was charged on two separate courts for a host of foreign-based financial schemes before he agreed to cooperate with the government.

In a short statement just before sentencing, Gates said he was sorry for what he’d done and asked for leniency for himself on behalf of his family.

“I accept complete responsibility for my actions,” Gates said.

Gates is mentioned more than 100 times in Mueller’s lengthy report, and his description of key events appears throughout.

He had faced up to 10 years in prison for the conspiracy and false statements counts he pleaded guilty to, but sentencing guidelines suggested a range of roughly four to five years because he had no prior criminal history. Both Gates and the Department of Justice asked the judge to use her discretion to cut that down to zero.

Jackson said Gates had been in 50 meetings with prosecutors and investigators, admitted things to the DOJ it wouldn’t have otherwise known, testified in three cases already, and promised to continue to cooperate.

But Jackson also noted that the crimes Gates had admitted to took place over a “substantial period of time,” included “a substantial amount of money,” and dealt with a “substantial number of lies.”

“So while I can’t say it was just a mistake” for Gates to commit these crimes, Jackson said, “it’s not as if it’s been a quick foray or a dipping of the toe into repentance.”

“Ultimately, he cooperated fully and candidly,” said Jackson. “His cooperation has been extraordinary.”

Jackson specifically pointed to Gates’s testimony that Manafort had asked campaign polling data to be shared with Russian oligarch Oleg Deripaska, the light Gates shed about the June 2016 Trump Tower meeting between Trump campaign associates and a number of Russians, and the details he provided about the campaign’s interest in the WikiLeaks emails.

Gates also told the FBI that Manafort floated the idea that the hacking of the Democratic National Committee was "likely carried out by the Ukrainians, not the Russians" sometime during the 2016 presidential election. Trump brought up a debunked CrowdStrike conspiracy theory during his controversial July 25 phone call with Ukraine's president this year.

The DOJ said Gates provided “important testimony” in its successful prosecution of Manafort and “significant testimony” during the recent case against longtime Trump associate Roger Stone, who was convicted for lying to the House Intelligence Committee about his communications related to WikiLeaks and the Trump campaign.

Prosecutors claimed Gates “received pressure not to cooperate with the government, including assurances of monetary assistance” but that nevertheless, “his cooperation has been steadfast.” Recently-released FBI notes of a 2018 interview with Gates show he claimed he felt pressured by Manafort not to plead or cooperate on multiple occasions, with discussions with Manafort including talk of possible pardons and an outside legal defense fund.

Molly Gaston, the sole DOJ prosecutor present for the sentencing, was effusive in her praise for Gates's "extraordinary assistance" despite that intense pressure and did not oppose his request for probation.

Gates’s lawyer Tom Green pointed to the number of prosecutors and agents who had filled the first row of the courtroom, which included DOJ officials involved with a variety of Mueller-related cases, including Manafort, Craig, and Stone.

“I think they’re here for more than just curiosity,” Green said. “They’re here to recognize the contributions he made to their investigations.”

Andrew Weissmann, dubbed Mueller’s “pit bull” and the special counsel’s righthand man during the two-year investigation, attended the hearing, shaking hands with Gaston and then with Gates and his team, sharing a quick conversation and big smiles before it began.

Gates gave Mueller a window into all the meetings and conversations he was privy to during the 2016 presidential election, recounting interactions with Manafort, Stone, and many others, including a phone call allegedly between Trump and Stone about a WikiLeaks release of hacked Democratic emails, which became part of the DOJ’s successful prosecutions.

Gates also helped the DOJ in an unsuccessful spinoff case against former Obama White House counsel Greg Craig, who was charged with misleading the DOJ during its inquiry into whether he should’ve registered as a foreign agent of Ukraine, and “although Craig was acquitted, Gates’ testimony was corroborated and credible, and the government believes that Gates testified truthfully and completely in that case.”

During the Manafort and Craig trials, Gates provided an insider look at the shady world of U.S. lobbying in Ukraine, shedding light on the years of work he and Manafort had done on behalf of the corrupt pro-Kremlin Ukrainian President Viktor Yanukovych.

And during the Stone trial, Gates, along with former Trump campaign executive Steve Bannon, highlighted how much interest the Trump campaign had in the WikiLeaks emails. Gates also told Mueller that Trump told his campaign command to “get the emails," referring to 33,000 emails that former Secretary of State Hillary Clinton deleted or otherwise did not provide investigators looking into her private server.

Gates was initially charged alongside Manafort in D.C. federal court in 2017 on eight counts, including for violations of the Foreign Agents Registration Act for their work in Ukraine, failures to report income from overseas work, money laundering and tax fraud schemes, and lying to cover it up.

A superseding 32-count federal indictment was handed down in Virginia in 2018, where Gates was further charged with helping Manafort file false tax returns for years, lying about his own tax returns, bank fraud conspiracies, and more.

Gates entered into a deal with the DOJ the day after the Virginia charges, pleading guilty to two counts: to commit tax fraud, hide foreign accounts, and dodge registering as a foreign agent; and to making false statements to the FBI to cover-up Manafort’s unregistered Ukraine-related lobbying to Congress.

The DOJ dismissed the other charges against him.