In February 2018, Richard Gates appeared in a Washington federal courtroom to plead guilty to charges brought by Robert Mueller’s team, beginning his new life as a key cooperator in the special counsel’s Russia investigation.

Gates returned to the same courtroom Thursday to mark a new high point in his cooperation with prosecutors: testifying against Greg Craig, the prominent Washington attorney accused of misleading the Justice Department about his past work for Ukraine. Seated in the witness stand, next to U.S. District Judge Amy Berman Jackson of the District of Columbia, Gates was reminded of the plea agreement that landed him in court last year.