Manafort, 69, is the first defendant to go to court to fight charges stemming from Mueller's investigation into Russian interference in the 2016 presidential election.
But it was Gates' testimony that has generated the most drama, as the witness admitted embezzling hundreds of thousands of dollars from his boss, confessed to an extramarital affair and turned in spectacular fashion against a longtime mentor. Prosecutors had previously said that Manafort's interactions with Calk were the only part of the trial expected to overlap with his Trump campaign role.
Gates' earlier testimony on Tuesday, meanwhile, centered on how Ukrainian businessmen paid Manafort for his consultancy work. But he could be seen twitching under cross examination by Downing, blinking hard as he faced the defense lawyer and sucking in his lips.
But at another point Wednesday, Gates attempted to express remorse from the stand, saying "I've made many mistakes over many years". U.S. District court Judge T.S. Ellis III presides.
Prosecutors have a star witness in Gates, and they also have a wellspring of evidence.
Gates spent Monday afternoon and most of Tuesday morning corroborating prosecutors' version of events; the government's attorneys say Gates and Manafort used offshore bank accounts and wire transfers to hide money from the IRS as to avoid paying taxes.
On Tuesday, Downing straight out asked Gates: "After all the lies you've told and fraud you've committed, you expect this jury to believe you?" The defense moved on.
The topic came up as Kevin Downing, Manafort's defense attorney, hammered away at Gates' admitted habit of filing doctored expense reports in an attempt to paint Gates as self-motivated and untrustworthy.
"Did you tell the Federal Bureau of Investigation that there was hidden income in those accounts?" He also said he 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. Gates testified that he and Manafort knew they were committing crimes for years, saying they had stashed money in foreign bank accounts and falsified bank loan documents.
"In Cyprus, they were documented as loans".
Gates said it was a "very common method" for Dr. K and that, once the money was moved into the accounts, Manafort decided what to do with it.
Paul Manafort (L), former campaign chairman for U.S. President Donald Trump, in Washington, DC, U.S., December 11, 2017, and Rick Gates, former campaign aide to Trump, in Washington, U.S., December 11, 2017 are pictured in this combination photograph.
Manafort and Gates were the first two people indicted in Mueller's investigation into potential ties between Russian Federation and the Trump campaign.
Gates struck a deal with special counsel Robert Mueller in February, pleading guilty to one count of conspiracy against the United States and one count of making false statements to the Federal Bureau of Investigation.
During the trial's first week, Mr Trump lashed out publicly against Mr Mueller and said the entire effort should be stopped "right now". But Trump has shown interest in the proceedings, tweeting support for Manafort.
"No, they're not", Gates said. Gates testified that Manafort asked him to float Calk, who was on Trump's economic advisory council, for Secretary of the Army. Gates came on board the Trump campaign with Manafort and stayed for the duration of the campaign, later serving as deputy chairman for Trump's inaugural committee and then starting a pro-Trump PAC. "WTF", Manafort wrote to Gates in an email using a common shorthand to show exasperation after learning his projected tax payment for 2014.
Gates converted the 2015 DMP P&L to a Word document for Manafort, but there were spacing, font, and other discrepancies between that copy and the original.
Prosecutor Greg Andres pointed out that he had created a "loan forgiveness letter between Mr. Manafort and Mr. Manafort".
Update from the Paul Manafort trial: Rick Gates admitted... everything in testimony yesterday.