What rights does a defendant have in a trial of sentence enhancement allegations?

The lead opinion next asserts it is "relevant" that "many of the procedural protections that apply in a Penal Code section 1025 trial rest on statutory, not federal constitutional, grounds." (Lead opn., ante, at p. 859 of 66 Cal.Rptr.2d, at p. 1128 of 941 P.2d.) It is true that many of a criminal defendant's procedural rights in a trial of sentence enhancement allegations find their origins in either a statute or a decision of this court, and not in the federal Constitution. For example, a trial court has [16 Cal.4th 859] discretion to order a separate hearing to determine the truth of the prior convictions (People v. Calderon (1994) 9 Cal.4th 69, 36 Cal.Rptr.2d 333, 885 P.2d 83), and, whether or not the trial is bifurcated, the defendant is entitled to a jury (Pen.Code, 1025). The sentence enhancements must be pleaded and proved (see, e.g., Pen.Code, 667, subd. (c), 1170.12, subd. (a), 667.5, subd. (d)), and the defendant must answer the charge in open court (Pen.Code, 1025; see also Pen.Code, 969 1/2 [when prior conviction allegation is added to complaint after defendant has pleaded guilty, he must be arraigned on the allegations] ). The People bear the burden of proving the sentence enhancement beyond a reasonable doubt. (People v. Tenner (1993) 6 Cal.4th 559, 566, 24 Cal.Rptr.2d 840, 862 P.2d 840; see also Pen.Code, 1096 [applying standard of beyond a reasonable doubt to "criminal actions"].)