Gates, 46, was expected to be cross-examined for another hour by Manafort's attorney Kevin Downing before prosecutors get a second chance to try and undo some of the possibly damaging testimony he gave during their redirect.
Downing on Tuesday spent hours firing questions at Gates to impugn his credibility and paint him as a liar, asking about everything from his extramarital affair in London and funds he embezzled from Manafort, to questions on whether he may have crossed the line by submitting personal expenses when he worked for Trump's inaugural committee.
Gates, who pleaded guilty in Special Counsel Robert Mueller's investigation in February, has testified that he helped Manafort falsify his tax returns, lie to banks to get loans and hide foreign bank accounts that Manafort used to receive payments from oligarchs for political work he did in Ukraine.
Manafort's defense team's primary strategy has been to pin much of the blame for financial crimes on Gates, and some observers felt Downing made some headway toward that goal on Tuesday.
"I think Gates was a very poor witness... I thought he was needlessly evasive and argumentative," said Barbara McQuade, a former US Attorney in Michigan who has been watching the trial and said she observed jurors reacting with negative body language as he testified.
However, she added, she still believes the government has a strong chance of winning.
"I think the jury will hate [Gates], but they should still convict [Manafort] because of the testimony of other witnesses and the other documents that do put all of this on Manafort."
Manafort, who served briefly as Trump's campaign manager in 2016, has pleaded not guilty.
In the six days since the trial began, the jury has heard from 15 witnesses including two of Manafort's former accountants and his former bookkeeper.