What is the test for dismissing an indictment for alleged prosecutorial misconduct?

We review de novo the district court's refusal to dismiss an indictment for alleged prosecutorial misconduct. United States v. Spillone, 879 F.2d 514, 520 (9th Cir.1989), cert. denied, 498 U.S. 878 (1990). A defendant who challenges an indictment bears a heavy burden to show misconduct. United States v. Venegas, 800 F.2d 868, 869 (9th Cir.1986), cert. denied, 479 U.S. 1100 (1987). "An indictment may be dismissed for prosecutorial misconduct only upon a showing of 'flagrant error' that significantly infringes on the ability of the grand jury to exercise independent judgment and actually prejudices the defendant." United States v. Larrazolo, 869 F.2d 1354, 1357 (9th Cir.1989).