Is a jury's failure to instruct on the element of sexual assault a constitutional error?

Although failure to instruct on this element of the crime is constitutional error, it is subject to the harmless error rule. See United States v. Harrison-Philpot, 978 F.2d 1520, 1526 (9th Cir.1992), cert. denied, --- U.S. ----, 113 S.Ct. 2392, 124 L.Ed.2d 294 (1993). This court has formulated the appropriate inquiry as follows: (1) "based on the instructions given, what must the jury have found to convict?" and (2) "in making those findings, did it necessarily find all the required elements of the charged crimes?" Id. (emphasis in original) (quotation omitted).