How have courts dealt with the issue of ambiguous hand gestures at trial?

Mendoza (2000) 24 Cal.4th 130, 179.) Appellant makes two arguments. First, he argues, "the hand gestures were too ambiguous to support anything more than a speculative inference of his guilt" and there was no substantial evidence to support the giving of that instruction. Second, he argues the instruction violates his right to due process. Appellant failed to object to the instruction at trial, therefore, he forfeited the instructional issue. (Cf. People v. Valdez (2004) 32 Cal.4th 73, 137.)