Does section 1025 of the California Criminal Code prohibit a jury from determining the truth of a prior conviction allegation from the remainder of the trial?

Although section 1025 does not prohibit a trial court from bifurcating the jury's determination of the truth of a prior conviction allegation from the remainder of the trial, it also does not expressly authorize such bifurcation. General authority to bifurcate trial issues may be found, however, in section [9 Cal.4th 75] 1044, which vests the trial court with broad discretion to control the conduct of a criminal trial: "It shall be the duty of the judge to control all proceedings during the trial ... with a view to the expeditious and effective ascertainment of the truth regarding the matters involved." (See People v. Cox (1991) 53 Cal.3d 618, 700, 280 Cal.Rptr. 692, 809 P.2d 351.) "The object of a trial is to ascertain the facts and apply thereto the appropriate rules of law, in order that justice within the law shall be truly administered. It is not only the right but the duty of a trial judge to so supervise and regulate the course of a trial that the truth shall be revealed in so far as it may be, within the established rules of evidence." (People v. Mendez (1924) 193 Cal. 39, 46, 223 P. 65.)

Having a jury determine the truth of a prior conviction allegation at the same time it determines the defendant's guilt of the charged offense often poses a grave risk of prejudice. As this court has recognized: "Evidence that involves crimes other than those for which a defendant is being tried is admitted only with caution, as there is the serious danger that the jury will conclude that defendant has a criminal disposition and thus probably committed the presently charged offense. [Citations.]" (People v. Thompson (1988) 45 Cal.3d 86, 109, 246 Cal.Rptr. 245, 753 P.2d 37.)