What is the current state of the law in the 9th Circuit regarding credibility of evidence presented to a grand jury?

Tham's contentions are meritless. The general rule in this circuit is that no independent inquiry will be made into the kind of evidence presented to a grand jury, when a duly constituted grand jury returns an indictment valid on its face. United States v. Basurto, 497 F.2d 781, 785 (9th Cir. 1974). We have held that a grand jury need not be advised of all matters concerning credibility, and that dismissal of the indictment is only required in extreme situations, as where the prosecutor knowingly presents perjured testimony. United States v. Thompson, 576 F.2d 784, 786 (9th Cir. 1978). No such situation exists in the instant case.