Gates, who is expected to continue testifying for several hours Tuesday, has been regarded as a crucial witness for the government ever since he pleaded guilty this year to two felony charges and agreed to cooperate in special counsel Robert Mueller's investigation into possible ties between Russian Federation and the Trump campaign.
On Friday, a tax preparer named Cindy Laporta admitted that she helped disguise $900,000 in foreign income as a loan in order to reduce Manafort's tax burden. The other four include an insurance agent, two bankers who worked on mortgages for Manafort, and Conor O'Brien, a former assistant to Laporta at the accounting firm KWC.
The longtime deputy to Paul Manafort was called to the witness stand Monday to testify against the former Trump campaign chairman in his financial fraud trial. Among those were seven transfers the government says were sham "loans" Manafort used to disguise millions in income from the IRS.
As late as August 2016 - the same month he resigned from the Trump campaign - Manafort was sending emails to Laporta asking her to alter a profit-and-loss statement for his company.
The courtroom testimony brought Gates face-to-face with Manafort, his longtime boss and fellow Trump campaign aide, for the first time since his plea deal. But Trump has shown interest in the proceedings, tweeting support for Manafort and suggesting he had been treated worse than gangster Al Capone.
The trial on Thursday was primarily dedicated to testimony about the nitty gritty of Manafort's business and personal finances, a shift from earlier in the week when prosecutors focused more on the details of Manafort's lavish spending on Land Rovers, ostrich jackets, designer suits and real estate.
But prosecutors for Special Counsel Robert Mueller, who charged Manafort with bank and tax fraud, hadn't provided much direct evidence through Friday to back their claims that he controlled the foreign shell companies that funded those purchases.
The defense plans to paint Gates as en embezzler willing to bend the truth because of the leniency he received in the plea bargain.
Gates, who also served in a senior role in Donald Trump's presidential campaign, is expected to face aggressive cross-examination once prosecutors are finished questioning him.
The testimony is expected to be the second day that prosecutors will present the jury detailed financial evidence they say proves Manafort cheated US tax authorities out of millions in undeclared income he earned working for pro-Russian politicians in Ukraine and lied to banks to get loans. He has played those roles throughout the trial, repeatedly scolding prosecutors to rein in their depictions of Manafort's lavish lifestyle and demanding that they "move it along". It is not a crime, he has said several times, to be rich and to spend ostentatiously. He also admitted to concealing millions of dollars in foreign bank accounts on Manafort's behalf and to falsifying documents to help his former boss obtain millions of dollars more in bank loans.
Gates told jurors that he siphoned off the money without Manafort's knowledge by filing false expense reports. When he stopped working as a consultant for Ukrainian officials, Manafort lied to banks about his income to obtain loans to finance his "extravagant lifestyle", prosecutors allege.
It was one of several times that Laporta testified that she accepted questionable financial statements pressed on her by Gates or Manafort, including some involving other loans prosecutors say were shams to hide income.
When they appeared, the bookkeeper and accountants said, they thought the companies were clients or, in some cases, lenders.
A defence lawyer for Manafort encouraged jurors in his opening statement to consider whether prosecutors had enough evidence to begin an audit of Manafort.
Prosecutors are giving more insight into how they built their case against former Trump campaign chairman Paul Manafort.