What is the test for determining whether a defendant has a mental capacity to stand trial?

"'Both federal due process and state law require a trial judge to suspend trial proceedings and conduct a competency hearing whenever the court is presented with substantial evidence of incompetence, that is, evidence that raises a reasonable or bona fide doubt concerning the defendant's competence to stand trial. [Citations.] . . . Evidence of incompetence may emanate from several sources, including the defendant's demeanor, irrational behavior, and prior mental evaluations.'" (Sattiewhite, supra, 59 Cal.4th at p. 464; accord, People v. Rogers, supra, 39 Cal.4th at p. 847.) Pursuant to

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section 1368, if the trial court and defense counsel express a doubt as to the defendant's competence to stand trial, the court must hold a competency hearing to determine the question of the defendant's mental competence in accordance with the specific procedures mandated by section 1369.⁶ (See, e.g. People v. Hale (1988) 44 Cal.3d 531, 541 ["once a doubt has arisen as to the competence of the defendant to stand trial, the trial court has no jurisdiction to proceed with the case against the defendant without first determining his competence in a section 1368 hearing"].)