Cite as: 505 U. S. 437 (1992)
Opinion of the Court
(1960) (per curiam). The entry of a plea of not guilty by reason of insanity, by contrast, presupposes that the defendant is competent to stand trial and to enter a plea. Moreover, while the Due Process Clause affords an incompetent defendant the right not to be tried, Drope v. Missouri, supra, at 172-173; Pate v. Robinson, supra, at 386, we have not said that the Constitution requires the States to recognize the insanity defense. See, e. g., Powell v. Texas, 392 U. S. 514, 536-537 (1968).
Under California law, the allocation of the burden of proof
to the defendant will affect competency determinations only in a narrow class of cases where the evidence is in equipoise; that is, where the evidence that a defendant is competent is just as strong as the evidence that he is incompetent. See United States v. DiGilio, 538 F. 2d 972, 988 (CA3 1976), cert. denied, 429 U. S. 1038 (1977). Our cases recognize that a defendant has a constitutional right "not to be tried while legally incompetent," and that a State's "failure to observe procedures adequate to protect a defendant's right not to be tried or convicted while incompetent to stand trial deprives him of his due process right to a fair trial." Drope v. Missouri, 420 U. S., at 172, 173. Once a State provides a defendant access to procedures for making a competency evaluation, however, we perceive no basis for holding that due process further requires the State to assume the burden of vindicating the defendant's constitutional right by persuading the trier of fact that the defendant is competent to stand trial.
Petitioner relies upon federal- and state-court decisions which have said that the allocation of the burden of proof to the defendant in these circumstances is inconsistent with the rule of Pate v. Robinson, supra, at 384, where we held that a defendant whose competence is in doubt cannot be deemed to have waived his right to a competency hearing. E. g., United States v. DiGilio, supra, at 988; People v. McCullum, 66 Ill. 2d 306, 312-314, 362 N. E. 2d 307, 310-311 (1977); State
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