In People v. Pollock (2004) 32 Cal.4th 1153, the trial court excluded testimony by the defendant's drug addiction expert concerning how the "'binge cycle or pattern of use and abuse applied specifically to defendant in the days'" surrounding the murders. The Supreme Court concluded the "trial court applied well-established state law principles governing expert testimony. 'When expert opinion is offered, much must be left to the trial court's discretion.' Although an expert may base an opinion on hearsay, the trial court may exclude from the expert's testimony 'any hearsay matter whose irrelevance, unreliability, or potential for prejudice outweighs its proper probative value.'Here, the trial court acted within its discretion in preventing the expert from expressing an opinion on whether defendant's conduct immediately before, during, and after the charged crimes was consistent with the binge pattern of crack cocaine use. That opinion would necessarily be based in large part on defendant's hearsay statements to the expert during an interview four years after the events in question." (Id. at p. 1172.) The court held that "to avoid putting this potentially self-serving and unreliable hearsay before the jury, without defendant ever having testified and submitted to cross-examination," the trial court could properly require the defense to proceed by the use of hypothetical questions. (Ibid.)