What is the sufficiency of evidence in the context of an allegation of sexual assault?

The thrust of appellants' arguments on the sufficiency of evidence is that the evidence against them is circumstantial. There is, nevertheless, more than enough evidence, direct, testimonial, and circumstantial, to establish beyond a reasonable doubt "an agreement to accomplish an illegal objective, coupled with one or more overt acts in furtherance of the illegal purpose and the requisite intent necessary to commit the underlying substantive offense." United States v. Oropeza, 564 F.2d 316, 321 (9th Cir. 1977), cert. denied, 434 U.S. 1080, 98 S.Ct. 1276, 55 L.Ed.2d 788 (1978).