What is the test for reversal of a finding of inadequate evidence in a sexual assault case?

In People v. Guiton (1993) 4 Cal.4th 1116, 17 Cal.Rptr.2d 365, 847 P.2d 45, we distinguished cases in which the prosecution relied on a factually [15 Cal.4th 38] inadequate theory from those in which the prosecution's theory was legally inadequate. We held that if the inadequacy of proof is purely factual, "reversal is not required whenever a valid ground for the verdict remains, absent an affirmative indication in the record that the verdict actually did rest on the inadequate ground." (Id. at p. 1129, 17 Cal.Rptr.2d 365, 847 P.2d 45.) We further held that if the inadequacy is legal, the "rule requiring reversal applies, absent a basis in the record to find that the verdict was actually based on a valid ground." (Ibid., fn. omitted.)