Is it misconduct for a prosecutor to ask for comments on the veracity of witnesses or the guilt of a defendant?

It is misconduct for a prosecutor to elicit comments on the veracity of witnesses or the guilt of the defendant. See, e.g., United States v. Combs, 379 F.3d 564, 572 (9th Cir.2004) (finding error where prosecutor asked defendant to testify that government agent was lying); United States v. Henke, 222 F.3d 633, 642 (9th Cir.2000) (finding that admission of testimony that defendants "must have known" of misconduct was erroneous). Nothing of the sort occurred here; Sherman never referred to a single witness or discussed the veracity of witnesses generally. That an expert reaches a conclusion that either agrees with or conflicts with that of a witness whose testimony he incorporated into his conclusions, does not without more constitute vouching. There was no error.