What is the test for determining whether a defendant is competent to stand trial?

The trial court stated a doubt as to defendant's mental competency and pursuant to section 1368 ordered a hearing to determine whether he was competent to stand trial. The hearing was never held. Section 1368, subdivision (c) states: "[W]hen an order for a hearing into the present mental competence of the defendant has been issued, all proceedings in the criminal prosecution shall be suspended until the question of the present mental competence of the defendant has been determined." (Italics added.) Under the clear language of section 1368, the trial court had no jurisdiction to proceed on the charges against defendant until the court determined whether defendant was competent to stand trial. ( People v. Hale, supra, 44 Cal.3d 531, 541, 244 Cal.Rptr. 114, 749 P.2d 769.) The trial court did not state the reason why the competency hearing was not held, and we need not and may not properly speculate as to the reason. That the hearing was not held is dispositive. We also need not repeat in detail the principles so recently set forth in Hale. In the interest of providing guidance, however, for further proceedings in this case and for other cases in which a question as to a defendant's competency arises, we explain why the most likely reasons for the failure to hold a competency hearing do not require a different result.