Former FBI lawyer James Baker, a star witness for the prosecution in the trial of former Hillary Clinton campaign lawyer Michael Sussmann, has taken the stand. Sussmann is accused of lying to Baker at a meeting back in September 2016, less than two months before that year’s presidential election.

At that meeting, Sussmann provided Baker with computer data Sussmann said showed a potential secret communications channel between a Russia-based bank and the Trump Organization, the company of then-candidate Donald Trump. Sussmann is accused of saying he was not presenting the computer data on behalf of a particular client. Prosecutors alleged Sussmann was not only representing the interests of the Clinton campaign and another client but also a technology executive who had provided him with the data.

Testifying Thursday, Baker said he was “100 percent confident” Sussmann told Baker he was not acting on behalf a particular client during the meeting.