Does the prosecution have the right to charge a defendant with murder in conjunction with a closely related crime?

Our research has disclosed no decision addressing the court's key legal determination, namely, that the exception applies when the prosecution exercised due diligence in its investigation and had probable cause to charge a defendant with murder in conjunction with a closely related crime, but deferred filing the murder charge until it acquired evidence supporting the objectively reasonable belief that it could sustain a murder conviction. Nonetheless, we find guidance from United States v. Stearns (9th Cir.1983) 707 F.2d 391 (Stearns ).