Can a criminal defendant waive his right to a jury trial on a prior conviction that has been alleged as a sentence enhancement?

Additionally, the right to a jury trial on a prior conviction that has been alleged as a sentence enhancement arises under a statute (Pen Code, 1025), and is not protected by the state or federal Constitution. (People v. Vera (1997) 15 Cal.4th 269, 277.) So far as we know, no court has ever held that the right of a criminal defendant to waive an appearance at a proceeding that is not constitutionally mandated, not usually sought, and not likely to present a close factual question, is nevertheless so momentous that it cannot be waived by counsel on behalf of the defendant.

Due process requires a trial court to conduct a competency hearing pursuant to section 1367 when there is substantial evidence that the defendant is incompetenti.e., that he or she lacks the ability to consult with counsel with a reasonable degree of rational understanding and a rational, as well as a factual understanding of the proceeding against him or her. (Godinez v. Moran (1993) 509 U.S. 389, 394; Pen. Code, 1367.)

The record contains two factors that might conceivably raise doubt about appellant's competency.