Gates, the government's star witness in Manafort's financial fraud trial, testified how, at the behest of his longtime boss, he helped hide millions of dollars in foreign income and submitted fake mortgage and tax documents.
Welch had told jurors that Manafort didn't report at least $16 million on his tax returns between 2010 and 2014.
During cross examination, defense attorney Downing tried to undermine Gates' credibility, noting the benefits he had gotten from his deal with the government, the fact that he made a false statement to investigators, his "scheme" to embezzle from Manafort, and even his "secret life" with a mistress.
The sidebar conversation - which the court's stenographer could hear, but which Gates, the jury and reporters in the room could not - came after Manafort attorney Kevin Downingasked Gates if he'd spoken to the special counsel's team about his time at the Trump campaign.
Earlier on Tuesday, the prosecution had continued to question Gates, who described how millions of dollars were allegedly funnelled from entities controlled by Ukrainian businessmen into Manafort's shell companies in Cyprus.
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.
U.S. District Judge T.S. Ellis III has interrupted prosecutors throughout the trial to encourage them to speed things along.
But Gates did not answer Downing's question after the prosecution objected to the relevance of the inquiry. "But Mr. Manafort was a longtime client of the firm, and I didn't think I should do that".
She said in another instance, Manafort maintained that there were no mortgages on a separate NY property when there actually were. "I was probably wrong in that", Ellis said to kick off the trial proceedings Thursday morning.
He showed jurors how the Federal Bureau of Investigation had painstakingly traced wire transfers from foreign bank accounts to retailers in the United States who sold Manafort expensive goods - including the custom men's clothier Alan Couture, where Manafort bought jackets made of ostrich and python skin that each cost five figures.
Ellis questioned whether prosecutor Greg Andres could shorten his case and skip some of the evidence.
A man prosecutors say has ties to Russian intelligence was also among the beneficial owners of some of the companies.
After wrapping up the tax portion of their case, prosecutors have moved on to bankers who were involved in extending Manafort loans during his scramble to generate cash in 2015 and 2016 after work dried up following a loss of business in Ukraine.
He told jurors how he disguised millions of dollars in foreign income as loans in order to lower Mr Manafort's tax bill. Trump himself has closely watched Manafort's trial as he continues to fume publicly about Mueller's investigation.
The terms of Manafort's loan also allowed him to withdraw cash from the bank, and Miceli testified that was not allowed for loans against investment properties.
On Thursday, a series of bank employees told jurors about discrepancies and outright falsehoods contained on Manafort's applications for millions of dollars in loans.
Ellis lost his cool at the start of Special Agent Michael Welch's testimony, after the government witness said he had been in the courtroom for some of the trial. Prosecutors allege Manafort used various ways to hide his income, including wiring money from Ukraine to the United States via a bank in Cyprus and listing it as a loan, and laundering almost $1 million through the purchases of Oriental rugs.
"I'm here. I'm trying to change", he said.