This was the testimony that close watchers of Manafort’s troubles have been waiting for since Gates flipped in February. Murmurs ran through the courtroom when prosecutors said they would call Gates to the stand at 4:15 pm, about an hour before the court proceedings typically end for the day. Gates, clean-shaven for his first public appearance since his guilty plea, did not look at his former boss, though Manafort followed his every step and answer.

“I was the one who helped organize the paperwork and initiate the wire transfers,” Gates said, describing Manafort’s use of unregistered Cypriot bank accounts to collect political consulting payments from Ukrainian oligarchs.

Gates also said he had filed false expense reports when he worked for Manafort as a way to steal hundreds of thousands of dollars from those accounts.

The admissions from Manafort’s so-called “right-hand man” gripped the courtroom, even though much of them had been previously known.

2. Gearing up for Tuesday

Gates will return to finish testifying Tuesday morning at 9:30, in what may be the true fireworks of the trial.

When he finished speaking Monday, he had described his history of work with Manafort, his plea deal with prosecutors and how Manafort’s consulting operation in Ukraine functioned. While Gates had already admitted to knowingly hiding foreign accounts for Manafort, there are still a lot of details about alleged fraud in Manafort’s indictment that prosecutors will want to ask him about. Gates was closely involved in much of Manafort’s interactions with his accountants and the banks.

Prosecutors said they still have about three hours of questions for Gates. In that time, we’re also likely to see several emails and other documents with Gates’ and Manafort’s names on them as evidence.

3. The art of the cross

Once Gates has walked through all the prosecutors’ evidence, the defense will begin its questioning of him.

In what’s known as a cross-examination, defense attorneys get to hurl questions at witnesses that could make the jury doubt the certainty of the prosecutors’ case. For instance, on Monday, after federal financial crimes specialist Paula Liss testified that neither Manafort nor his wife had reported foreign bank accounts to her agency, FinCEN, defense attorney Tom Zehnle asked her if a person owning less than 51 percent of a company would need to report those accounts. She said no, explaining a technicality, and leaving the possibility hanging in the air that Manafort and his wife, who split ownership of DMP International, may not have needed to make the disclosures.