Rick Gates, a associate of US President Donald Trump's former campaign chairman Paul Manafort, testified Monday that they committed crimes together.
Gates's appearance in court marked a dramatic moment in the probe: the first visible case of a witness flipping, or turning on friends or colleagues in a case.
Manafort did not stare Gates down as he did on Monday.
In opening arguments, Manafort's lawyer defended his client by blaming Gates for the offenses alleged against his client. "In reality, it was basically money moving between accounts", Gates said. He said he engaged in the wrongdoing at Mr Manafort's direction. He described how they also transferred money from their Cypriot bank accounts to a bank in the Caribbean.
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. He also said he may have submitted personal expenses for reimbursement by Trump's inaugural committee, which he helped operate.
Like several of the witnesses who appeared last week, Gates said Manafort was "one of the most politically brilliant strategists I've ever worked with".
"In Cyprus, they were documented as loans".
Manafort disliked paying a lot of taxes, Gates said.
Gates has been described by witnesses as Manafort's right-hand man who helped run the operations of a multimillion-dollar political consulting business.
He said he was aware Mr Manafort was acting as an unregistered foreign agent in lobbying for Ukraine.
Gates' statements reinforced that picture. Kerik, on the other hand, isn't putting any weight on Gates' words because of his motivation for testifying. "We didn't report the income or the fact that the accounts existed".
He said Manafort asked for tickets to Trump's inauguration so he could give them to a banker involved in approving a loan at the centre of his financial fraud trial. They aimed to show jurors how that money flowed from more than a dozen shell companies used to stash the income in Cyprus.
Gates did not make eye contact with Manafort as he took the stand wearing a yellow tie and navy blue suit.
On Monday Gates testified that he has met with prosecutors about 20 times. He said his own crimes included cheating on his taxes and lying to Federal Bureau of Investigation agents just weeks before he pleaded guilty in February to conspiracy and false statements.
Andres said he was obligated to show the jury why Manafort was getting tens of millions of dollars in payments to prove it was income.
Downing also accused Gates of embezzling "millions", a higher amount than Gates later admitted to in his testimony.
It is unclear how long the arrangement extended.
Gates began working for Manafort in 2006 on his business ventures in Ukraine.
Gates said he did, but the defence lawyer wasn't satisfied. The party won seats in an October 2014 parliamentary election; Gates testified that the work ended then. The charges largely predate his five months on the Trump campaign.