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

If the trial judge doubts the defendant's competency to stand trial, the judge is required to state that doubt on the record. ( 1368, subd. (a).) "This is the first step in initiating formal proceedings to determine a defendant's competence to stand trial." (People v. Price (1991) 1 Cal.4th 324, 396.) But the judge's "expression of preliminary concerns about [a defendant's] competency" does not require the court to commence competency proceedings. (Id. at pp. 396-397.) Absent a showing of incompetence that is substantial as a matter of law, the trial court's decision not to order a competency hearing is entitled to great deference on appeal. (People v. Rogers, supra, 39 Cal.4th at p. 847.)

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