When prosecutorial misconduct is so flagrant that a grand jury indictment can be dismissed on supervisory power grounds?

6 Reviewing courts have not always clearly articulated their rationale for determining when prosecutorial misconduct is so flagrant that dismissal of an indictment is warranted. Our court, for example, has suggested that indictments may be dismissed on supervisory power grounds only when there is a "clear basis in fact and law" for judicial intervention into the grand jury process, United States v. Chanen, 549 F.2d 1306, 1313 (9th Cir.), cert. denied, 434 U.S. 825, 98 S.Ct. 72, 54 L.Ed.2d 83 (1977). We confess this standard is so vague and conclusory that it fails to illuminate the applicable legal principles, and provides district judges who are called upon to apply it precious little guidance.