Is a defendant mentally competent to stand trial?

" 'Both the due process clause of the Fourteenth Amendment to the United States Constitution and state law prohibit the state from trying or convicting a criminal defendant while he or she is mentally incompetent. ( 1367[, subd. (a) (noting in relevant part that a "person cannot be tried or adjudged to punishment . . . while that person is mentally incompetent," and further noting 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")]; Drope v. Missouri (1975) 420 U.S. 162, 181; Pate v. Robinson (1966) 383 U.S. 375, 384-386; People v. Ramos (2004) 34 Cal.4th 494, 507.) A defendant is incompetent to stand trial if he or she lacks a ' "sufficient present ability to consult with his lawyer with a reasonable degree of rational understanding [or lacks] . . . a rational as well as a factual understanding of the

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