Can an expert be cross-examined as to a defendant's out-of-court statements?

Defendant cites no case, and our research has found none, holding that a court "violated" Evidence Code section 721 by precluding cross-examination of an expert witness as to a defendant's out-of-court statements that were reviewed by the expert. Under Evidence Code section 721, a witness who testifies as an expert may, of course, be cross-examined to the same extent as any other witness. While the scope of cross-examination of an expert is "broad" (People v. Doolin (2009) 45 Cal.4th 390, 434), it is not boundless.