What is the test for a motion to dismiss Rule 48(a) of the Criminal Code?

5 Rule 48(a) provides that prosecutors may, "by leave of court," file a dismissal of an indictment, information or complaint. A court is generally required to grant a prosecutor's Rule 48(a) motion unless dismissal is "clearly contrary to manifest public interest." United States v. Cowan, 524 F.2d 504, 513 (5th Cir.1975), cert. denied, 425 U.S. 971, 96 S.Ct. 2168, 48 L.Ed.2d 795 (1976); accord United States v. Carrigan, 778 F.2d 1454, 1463 (10th Cir.1985); United States v. Miller, 722 F.2d 562, 566 (9th Cir.1983).