Before petitioner Medinas trial for, inter alia, first-degree murder, the California court granted his motion for a competency hearing pursuant to a state law that forbids a mentally incompetent person to be tried or punished, establishes a presumption of competence, and placed on petitioner the burden of proving incompetence by a preponderance of the evidence. The jury empaneled for the competency hearing found Medina competent to stand trial and, subsequently, he was convicted and sentenced to death. The State Supreme Court affirmed, rejecting Medinas claim that the competency statutes burden of proof and presumption provisions violated his right to due process.

Held:

1. The Due Process Clause permits a State to require that a defendant claiming incompetence to stand trial bear the burden of proving so by a preponderance of the evidence. Pp. 442-453.

(a) Contrary to Medinas argument, the Mathews v. Eldridge, 424 U.S. 319, test for evaluating procedural due process claims does not provide the appropriate framework for assessing the validity of state procedural rules that are part of the criminal law process. It is not at all clear that Mathews was essential to the results in United States v. Raddatz, 447 U.S. 667, or Ake v. Oklahoma, 470 U.S. 68, the only criminal law cases in which this Court has invoked Mathews in resolving due process claims. Rather, the proper analytical approach is that set forth in Patterson v. New York, 432 U.S. 197, in which this Court held that the power of a State to regulate procedures for carrying out its criminal laws, including the burdens of producing evidence and persuasion, is not subject to proscription under the Due Process Clause unless "`it offends some principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental." Id., at 201-202. Pp. 442-446.

(b) There is no historical basis for concluding that allocating the burden of proof to a criminal defendant to prove incompetence violates due process. While the rule that an incompetent criminal defendant should not be required to stand trial has deep roots in this countrys common law heritage, no settled tradition exists for the proper allocation of the burden of proof in a competency proceeding. Moreover, contemporary [505 U.S. 437, 438] practice demonstrates that there remains no settled view on where the burden should lie. Pp. 446-448.

(c) Nor does the States allocation of the burden of proof to a defendant transgress any recognized principle of "fundamental fairness" in operation. This Courts decision in Leland v. Oregon, 343 U.S. 790 - which upheld a States right to place on a defendant the burden of proving the defense of insanity - does not compel the conclusion that the procedural rule at issue is constitutional, because there are significant differences between a claim of incompetence and a plea of not guilty by reason of insanity. Nonetheless, once the State has met its due process obligation of providing a defendant access to procedures for making a competency evaluation, there is no basis for requiring it to assume the burden of vindicating the defendants constitutional right not to be tried while legally incompetent by persuading the trier of fact that the defendant is competent to stand trial. Pp. 448-449.

(d) Allocating the burden to the defendant is not inconsistent with this Courts holding in Pate v. Robinson, 383 U.S. 375, 384, that a defendant whose competence is in doubt cannot be deemed to have waived his right to a competency hearing, because the question whether a defendant whose competence is in doubt can be deemed to have made a knowing and intelligent waiver is quite different from the question presented here. Although psychiatry is an inexact science and reasonable minds may differ as to the wisdom of placing the burden of proof on the def