Mr Downing forced Gates to admit he had stolen hundreds of thousands of dollars from Manafort by filing bogus personal expenses claims and that he had engaged in an extramarital affair and kept an apartment in London for that objective.
Downing also ventured into territory both sides had agreed to avoid: discussion of Donald Trump's presidential campaign.
Gates said he did not. But then prosecutor Greg Andres invoked Trump's name, and Gates' and Manafort's work on the campaign became more explicitly tied to the alleged crimes at the heart of the trial.
The judge then brought the trial to a standstill late Tuesday afternoon, calling a brief recess.
Gates did stumble a few times on the stand.
Manafort's accountant was asked about a purported $10 million loan from Russian oligarch Oleg Deripaska. While Trump has not played a significant role in the trial, Gates testified on Tuesday that after the election, Manafort recommended a banker who had loaned him money to be Trump's Army secretary.
She said Manafort's passport was used to open many of them in U.S. dollars, euros and British pounds.
In detailed testimony, Gates has walked prosecutors through the step-by-step process on how he and Manafort doctored and backdated documents.
Wednesday's drama comes after Gates spent large chunks of Monday and Tuesday on the stand detailing a long list of crimes he and Manafort committed, sometimes together, sometimes separately. He was so desperate, prosecutors say, that he allegedly falsified loan application documents to keep himself afloat.
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In one exchange published in court Wednesday, Manafort instructs his Cypriot lawyer, Kypros Chrysostomides - referred to in court as "Dr. K" because, according to Gates, his name is hard to spell and pronounce - to transfer money from the Manafort-controlled Leviathan Ltd.
Special counsel Robert Mueller's team is reportedly asking Judge T.S. Ellis, who is overseeing the trial of former Trump campaign chairman Paul Manafort, to tell the jury he crossed the line by attacking prosecutors. "In reality, it was basically money moving between accounts". Before the final bang - or was it a whimper? - prosecutors had their own opportunity Wednesday morning to revisit with Gates exactly what he had done by way of financial crimes, and the steep, lifelong outcome of prison time he could face if he told the jury inaccuracies about Manafort.
Manafort, a longtime Republican political consultant, used the accounts to receive payments from Ukrainian oligarchs, the jury has heard.
She essentially connected the dots of testimony from previous witnesses - vendors, Manafort's bookkeeper and accountants, and Gates - but did so in a way that presented direct links between one witness's part of the story and another's.
An IRS agent says Paul Manafort didn't report at least $16 million in income on his taxes. Courtroom illustration courtesy of Bill Hennessy.
Mr. Gates admitted over three days to various crimes, including some he said he committed with Mr. Manafort and others he carried out on his own.
Prosecutors have noted that Gates and Manafort were not the targets of the investigation at the time of the interview.
"Yes, because I'm here to tell the truth and take responsibility for my actions", Gates replied. Andres prompted Gates to point out where the money came from that he had stolen. When the trial broke for lunch, Manafort looked back at his wife, sitting in the front row, smiled and winked at her, followed by a quick shake of his head, seeming to indicate he was unfazed by the morning's testimony.
Gates finally admitted that he had provided false information prior to striking a plea agreement. That, Downing said, would invalidate his plea deal.