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

present ability to consult with his lawyer with a reasonable degree of rational understandingand whether he has a rational as well as factual understanding of the proceedings against him."' [Citation.]" (Drope v. Missouri, supra, 420 U.S. at p. 172.) Under California statutory law, section 1367, subdivision (a), "A defendant is mentally incompetent for purposes of this chapter if, as a result of mental disorder or developmental disability, the defendant is unable to understand the nature of the criminal proceedings or to assist counsel in the conduct of a defense in a rational manner."

Our review is for substantial evidence. "The decision whether to order a competency hearing rests within the trial court's discretion, and may be disturbed upon appeal 'only where a doubt as to [mental competence] may be said to appear as a matter of law or where there is an abuse of discretion.' [Citation.] When the [trial] court is presented with 'substantial evidence of present mental incompetence,' however, the defendant is 'entitled to a section 1368 hearing as a matter of right.' [Citation.] On review, our inquiry is focused not on the subjective opinion of the trial judge, but rather on whether there was substantial evidence raising a reasonable doubt concerning the defendant's competence to stand trial. [Citation.] Evidence may be substantial even where it is contested or presented by the defense. [Citation.] A trial court reversibly errs if it fails to hold a competency hearing when one is required under the substantial evidence test. [Citation.]" (People v. Mickel, supra, 2 Cal.5th at p. 195.)