If a prosecutor takes part in grand jury proceedings in which a defendant gave false testimony, can he be found guilty of perjury?

he has first-hand knowledge of the events that culminated in a defendant's trial. See United States v. Regan, 103 F.3d 1072, 1083 (2d Cir. 1997) ("Standing alone, the mere fact that a prosecutor took part in grand jury proceedings in which a defendant presented false testimony should not bar that prosecutor from participating in a subsequent trial for perjury."). A problem arises, we have suggested, where there is some "indication in the record that [the prosecutor] sought to use [his] first-hand knowledge of [the] case to influence the jury." Id.