Gates, a former business partner of Manafort, testified that he began working with Manafort directly in October 2006, and the pair conspired between 2008 and 2015.
Gates pleaded guilty in February to one count of conspiracy against the United States and one count of lying to an Federal Bureau of Investigation agent in exchange for testifying against his former boss.
The case is being prosecuted by the special counsel investigating Russian interference in the 2016 USA presidential election.
Gates, who testified Monday and returned to the witness stand Tuesday, detailed years of alleged lawbreaking at Manafort's political firm and admitted to stealing money from secret overseas bank accounts.
For this Manafort was paid US$4million a year, in quarterly payments of US$1million, Gates recalled, though at some point the currency switched from USA dollars to Euros. And the fact that after loaning Manafort millions of dollars Calk became an economic adviser to Trump casts doubt on Trump's famous pledge to "drain the swamp" and puncture the rampant influence peddling in Washington. Gates was asked about 11 Cypriot accounts, and he testified that they were all owned by Ukrainian businessmen.
Undercutting Gates' credibility is the foundation of Manafort's defense. From 9:30 am until just after 3 pm, Gates corroborated the testimony of Manafort's bookkeeper and two accountants from the days before, along with prosecutors' evidence.
"Yes, this is approved", Manafort responded.
Sure, Gates called himself a liar and a cheat on Tuesday. The funds were logged as loans in order to meet later audits in Cyprus that required documentation of transfers between bank accounts.
Manafort is on trial here facing bank and tax fraud charges.
DMP International's revenue stream from Ukraine dried up in 2014 after its main client, former Ukrainian President Viktor Yanukovych, fled to Russian Federation amid a popular revolt.
"I'm here to tell the truth and take responsibility for my actions", Gates said in response to a question from Downing about his trustworthiness. But Trump has shown interest in the proceedings, tweeting support for Manafort.
That P&L showed DMP had lost $638,048 in the first half of the year.
Manafort returned an edited version of the P&L to Gates later that day.
For now, the defense team has largely left in tact the possibility that Manafort engaged in the crimes alongside Gates.
"After all the lies you've told and fraud you've committed, you expect this jury to believe you?" But Gates pleaded guilty months later and agreed to cooperate in Mueller's investigation of Manafort, the only American charged by the special counsel to opt for trial instead of a guilty plea. He also committed credit card and mortgage fraud, falsified a letter for a colleague involved in an investment deal and made false statements in a deposition at Manafort's direction.
The goal of the letter was to coax the Swiss company into investing in Brown's project as well.
"WTF? How could I be blindsided by this". He was aware that Manafort was acting as an unregistered foreign agent in lobbying for Ukraine, he said.
Gates' voice remained steady and calm throughout his roughy six hours of testimony Tuesday.
He has avoided the fierce stare of his former boss sitting arms folded in the defendant's chair, but his answers have been quick and stated clearly. "Mr Manafort worked with the local political officials and helped implement policy initiatives based on the campaign promises".
Gates repeatedly challenged Downing's characterization of certain events with astonishingly self-incriminating frankness.
In a dramatic moment before the jury, Manafort's defence counsel, Kevin Downing, put it to the government's star witness: "There's another life, right, the other Rick Gates?".
"It's not a secret life", Gates said.
"I haven't", Gates replied, explaining that the money went into his personal accounts and was spent over the years.
He also admitted to embezzling money from other employers in the past. Gates offered that he had been the recipient of an "unauthorized transaction".
"When did you start providing false and misleading information to the special counsel's office?" the defence counsel asked bluntly.
"What difference does it make?"
Andres followed up: "Did Mr Manafort know?"
When Downing questioned why Gates had embezzled money from his boss, he used it as an opportunity to issue a public apology.