Rick Gates is playing a key role in the trial of Paul Manafort, President Donald Trump’s former campaign manager who is currently facing tax and bank fraud charges.

Gates, Manafort’s former business associate, testified against his former boss on Monday, saying they committed crimes together.

Gates struck a plea deal with Special Counsel Robert Mueller to testify against Manafort in exchange for a potentially reduced sentence on his own charges. Gates was accused of “conspiracy against the United States, conspiracy to launder money, being an unregistered agent of a foreign principal, making false and misleading statements, and seven counts of failure to file reports of foreign banks and financial accounts,” according to Reuters,

Gates faces about five years in jail, unless a judge decides he provided “substantial assistance” to the special counsel. If convicted, Manafort, 69, could spend the rest of his life in jail, the The Washington Post says.

Gates began working for Manafort’s firm in the 1990s, but left for a period to pursue work in the gaming business. According to the Post, Gates began working for Manafort again in 2006, when the two became political consultants in Ukraine, earning tens of millions of dollars and managing their earnings through offshore accounts. Gates also worked with Manafort during Trump’s presidential campaign in 2016.

Prosecutors are trying to prove that Manafort, in his business dealings, repeatedly instructed Gates to lie, breaking the law in the process. Manafort’s attorney’s lay blame for any crimes on Gates, who lied to government officials even while trying to strike his plea deal, the Post reports.

Update: This article was updated with additional information from Rick Gates’ testimony.

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