Hypothetical questions posed to an expert must be based on the evidence; the questioner is not required to “disguise” the fact that such a question is based on the case evidence. Appellant and his codefendants were convicted of assault by means of force likely to inflict great bodily injury. The jury also found a gang enhancement true (Pen. Code, §186.22, subd. (b)(1)). Relying on People v. Killebrew (2002) 103 Cal.App.4th 644, the Court of Appeal found the prosecutor is prohibited from asking hypothetical questions using facts which closely track the case evidence. The Supreme Court disagreed, finding a hypothetical question posed to an expert must be rooted in the case evidence. A hypothetical question which is not based on the evidence “is irrelevant and of no help to the jury.” “To the extent that Killebrew . . . was correct in prohibiting expert testimony regarding whether the specific defendants acted for a gang reason,” the problem is not that such an opinion embraces an ultimate issue in the case, but that an expert’s opinion regarding the defendant’s guilt is of no assistance to the trier of fact, which is competent to weigh the evidence and reach a conclusion regarding guilt or innocence. The use of hypothetical questions based on the case evidence do not improperly invade the province of the jury, which still must decide whether to credit the expert’s opinion and determine whether the facts used to construct the hypothetical are the actual facts based on the evidence. The trial court did not err in allowing the prosecution to pose hypothetical questions based on the case evidence.