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

"If presented with 'evidence that raises a reasonable doubt about a defendant's mental competence to stand trial,' a trial court must suspend the criminal proceeding and hold a hearing to determine the defendant's mental competence. (People v. Elliot (2012) 53 Cal.4th 535, 583.) "Evidence of incompetence may emanate from several sources, including the defendant's demeanor, irrational behavior, and prior mental evaluations. [Citations.]" (People v. Rogers (2006) 39 Cal.4th 826, 847.) "[A] defendant must exhibit more than bizarre, paranoid behavior, strange words, or a preexisting psychiatric condition that has little bearing on the question of whether the defendant can assist his defense counsel." (People v. Ramos (2004) 34 Cal.4th 494, 508.) "A trial court's decision whether or not to hold a competence hearing is entitled to deference, because the court has the opportunity to observe the defendant during trial. [Citations.]" (People v. Rogers, supra, 39 Cal.4th at p. 847.)