I respectfully dissent.
As the majority opinion recognizes, this case presents a significant constitutional issue that has not yet been resolved by this court or by the United *915States Supreme Court and that has divided the lower federal courts and other state courts. The question is: When a doubt has arisen with respect to a criminal defendant’s competency to stand trial, is it constitutionally permissible for a state to apply a procedural rule that presumes the defendant is competent and that places on the defendant the burden of proving that he is incompetent? (See Pen. Code, § 1369, subd. (f).)1
I disagree with the majority’s conclusion that the challenged procedural rule is constitutional. Although the majority accurately note that “[t]he cases from other state and federal jurisdictions are in conflict on the constitutional propriety of placing on the defendant the burden of proving his own incompetence” (see maj. opn., ante, p. 882), the opinion fails to point out that the overwhelming majority of decisions, both federal and state, that have addressed the issue have held that in a competency proceeding it is the prosecution, rather than the defendant, that must properly bear the burden of proof on the competency issue. (See, e.g., United States v. DiGilio (3d Cir. 1976) 538 F.2d 972, 986-989; United States ex rel. Bilyew v. Franzen (7th Cir. 1982) 686 F.2d 1238, 1244-1245; Brown v. Warden, Great Meadow Correctional Facility (2d Cir. 1982) 682 F.2d 348, 351-354; United States v. Makris (5th Cir. 1976) 535 F.2d 899, 905-906; People v. McCullum (1977) 66 Ill.2d 306 [362 N.E.2d 307, 310-311]; State v. Jones (S.D. 1987) 406 N.W.2d 366, 367-370; State v. Bertrand (1983) 123 N.H. 719 [465 A.2d 912, 916-917]; Diaz v. State (Del. 1986) 508 A.2d 861, 863-864; State v. Heger (N.D. 1982) 326 N.W.2d 855, 857-858; Commonwealth v. Crowley (1984) 393 Mass. 393 [471 N.E.2d 353, 357-358]; Jolley v. State (1978) 282 Md. 353 [384 A.2d 91, 98]; contra Lowenfield v. Phelps (5th Cir. 1987) 817 F.2d 285, 294-295, affd. on other grounds (1988) 484 U.S. 231 [98 L.Ed.2d 568, 108 S.Ct. 546]; State v. Chapman (1986) 104 N.M. 324 [721 P.2d 392, 395]; State v. Pruitt (1984) 18 Ohio.App.3d 50 [480 N.E.2d 499, 509] (separate conc. opns. of Markus, J., and Nahra, J.); Wallace v. State (1981) 248 Ga. 255 [282 S.E.2d 325, 330]; State v. Aumann (Iowa 1978) 265 N.W.2d 316, 319-320.) While not all of the cases in the majority line are explicitly based on constitutional principles, a substantial number of the decisions clearly rest on a constitutional foundation. (See DiGilio, supra, 538 F.2d at p.988; Bilyew, supra, 686 F.2d at pp. 1244-1245; McCullum, *916supra, 362 N.E.2d at pp. 310-311; Jones, supra, 406 N.W.2d at pp. 369-370; Bertrand, supra, 465 A.2d at p. 916.) Thus, the majority, in sustaining the constitutional validity of a statutory provision that requires a defendant to bear the burden of proving his own incompetency, have chosen to align our court with the minority of courts that have addressed the issue.
I acknowledge, of course, that our resolution of the constitutional question cannot properly be based on a head count of what other courts have done, but must rest on our own considered evaluation of the merits of defendant’s constitutional claim. When the substance of the constitutional considerations underlying the out-of-state authorities is carefully analyzed, however, in my view it is clear that the opinion’s conclusion cannot be sustained.
As the majority opinion recognizes, the constitutional analysis must begin with the United States Supreme Court decisions in Pate v. Robinson (1966) 383 U.S. 375 [15 L.Ed.2d 815, 822, 86 S.Ct. 836] and Drope v. Missouri (1975) 420 U.S. 162 [43 L.Ed.2d 103, 112-113, 95 S.Ct. 896]. In Pate and Drope, the United States Supreme Court established that the federal due process clause not only prohibits a state from convicting a defendant who is not legally competent to stand trial, but also requires a state to adopt and to apply procedures that are fully adequate to protect this constitutional right. (See Pate, supra, 383 U.S. at p. 378 [15 L.Ed.2d at p. 818]; Drope, supra, 420 U.S. at pp. 171-172 [43 L.Ed.2d at pp. 112-113].) The question before us is whether a state procedure that places the burden of proof at the competency hearing on the defendant properly protects this crucial right.
In United States v. DiGilio, supra, 538 F.2d 972 (hereafter DiGilio), the Third Circuit identified two distinct considerations that render a rule placing the burden of proof of incompetency on a defendant constitutionally impermissible. The first consideration is the basic unfairness of placing the burden of proof on a defendant whose incompetence, if actually present, will impair his ability to adequately assist in the task of meeting his burden of proof. With respect to this point, the DiGilio court noted that in Pate v. Robinson, supra, 383 U.S. 375, the United States Supreme Court had rejected the notion that a defendant, as to whom a question of incompetency had arisen, could waive his right to have his competency determined prior to trial. The Supreme Court reasoned in Pate that “it is contradictory to argue that a defendant may be incompetent, and yet knowingly or intelligently ‘waive’ his right to have the court determine his capacity to stand trial.” (Pate, supra, 383 U.S. at p. 384 [15 L.Ed.2d at p. 821].) The DiGilio court explained that “[i]t is equally contradictory to argue that a defendant who may be incompetent should be presumed to possess sufficient intelligence *917that he will be able to adduce evidence of his incompetency which might otherwise be within his grasp.” (DiGilio, supra, 538 F.2d at p. 988.)
The second consideration emphasized by the DiGilio court is that a rule that places the burden of proof on the defendant means that when the evidence on the competency issue is equally balanced, the trier of fact must resolve the issue in favor of competency, thereby subjecting a defendant to a criminal proceeding in which he faces serious sanctions even when the defendant is as likely to be incompetent as competent. As the DiGilio court put it: “[W]hat we are determining is a rule of law, of due process dimensions, that a defendant, about whom the evidence of competency to stand trial is in equipoise, should or should not be tried. If, as the [Supreme] Court has made clear, the concept of competency to stand trial is grounded in notions of fundamental fairness in the operation of the judicial process, see Drope v. Missouri, supra, 420 U.S. at 171-172, 95 S.Ct. 896, the question can only be answered in the negative. Evidence showing competency must be more persuasive than that showing incompetency. Of necessity, then, there is no room for a rule of law placing any burden of proof on the defendant.” (DiGilio, supra, 538 F.2d at p. 988, fn. omitted.)
In rejecting defendant’s constitutional claim in the present case, the majority opinion relies almost entirely on the fact that the United States Supreme Court, in Leland v. Oregon (1952) 343 U.S. 790, 798-799 [96 L.Ed. 1302, 1308-1309, 72 S.Ct. 1002] (hereafter Leland), and Rivera v. Delaware (1976) 429 U.S. 877 [50 L.Ed.2d 160, 97 S.Ct. 226] (hereafter Rivera), has held that it is not unconstitutional for a state to impose on a defendant the burden of proof with respect to an insanity defense. Like the minority line of decisions it follows, however, the majority opinion fails to recognize that the Leland and Rivera decisions have no bearing whatsoever on either of the two constitutional problems identified in DiGilio, supra, 538 F.2d 972.
To begin with, the competency issue and the insanity issue deal with a defendant’s mental state at two entirely diiferent points in time. As one commentator has explained: “[T]he issue of incompetency to stand trial must be distinguished from . . . the defense of insanity in a criminal trial, where the question is whether the defendant’s mental condition at the time of the criminal act was such that he should not be held responsible for his conduct. The question of competency to stand trial relates rather to the appropriateness of conducting the criminal proceeding in light of the defendant’s present inability to participate effectively.” (Note, Incompetency to Stand Trial (1967) 81 Harv.L.Rev. 454, italics added.)
In the insanity context, a rule placing the burden of proof of insanity on the defendant imposes that burden on a defendant who, by necessity, must *918have already been found to be presently competent to assist in his own defense. When a defendant is presently competent, there may be no greater unfairness in placing the burden on the defendant to prove that he was insane at the time of the offense than there is in requiring such a defendant to bear the burden of proof with regard to other affirmative defenses.
In the competency context, by contrast, the defendant’s present ability to understand the proceeding and assist his counsel is the very matter in doubt, raising the fundamental problem of the potential unfairness of a rule that requires an incompetent defendant to shoulder the burden of proof on the crucial question of competency. Thus, the Supreme Court’s decisions in Leland, supra, 343 U.S. 790, and Rivera, supra, 429 U.S. 877, holding that it is constitutionally permissible to place on a presently competent defendant the burden of establishing an insanity defense, provide no logical or legal support for the proposition that it is constitutionally permissible to place the burden of proof on a defendant who may be presently incompetent to assist his counsel in meeting that burden.
Furthermore, Leland, supra, 343 U.S. 790, and Rivera, supra, 429 U.S. 877, are equally unresponsive to the second constitutional concern identified in DiGilio, supra, 538 F.2d 972, 988, namely, that a rule placing the burden of proof of competency on the defendant violates due process because it creates too great a risk of an unreliable competency determination by permitting a defendant to be found competent and subjected to trial even when the evidence of competence does not outweigh the evidence of incompetence.
In Leland, supra, 343 U.S. 790, and Rivera, supra, 429 U.S. 877, the burden of proof question arose in the context of the proper allocation of burdens of proof between the prosecution and the defense with regard to the elements of an offense, on the one hand, and affirmative defenses, on the other. In Leland and Rivera, and in the more recent decision in Martin v. Ohio (1987) 480 U.S. 228 [94 L.Ed.2d 267, 107 S.Ct. 1098], the United States Supreme Court reaffirmed the constitutionality of the general common law rule placing the burden of proving an affirmative defense on the defendant. These cases simply hold that so long as the prosecution is required to meet its burden of proving all the elements of a criminal offense beyond a reasonable doubt, the Constitution does not preclude a state from placing on the defendant the burden of proving an affirmative defense.
In the present case, unlike Leland, supra, 343 U.S. 790, Rivera, supra, 429 U.S. 877, or Martin v. Ohio, supra, 480 U.S. 228, the burden of proof question does not involve a matter of allocating burdens with respect to an element of an offense or an affirmative defense. While it is true, as the *919majority opinion observes, that a “defendant’s competence to stand trial . . . is no more an element of the crime charged than is his sanity” (see maj. opn., ante, p. 884), it is equally clear that the question of a defendant’s competency to stand trial is not an affirmative defense. Unlike an affirmative defense, the competency issue is not one that a defendant may raise or decline to raise at his own option. Once a question as to the defendant’s competency has arisen, the controlling Supreme Court decisions establish that, as a constitutional matter, the trial court must hold a hearing on the question even if the defendant objects and wishes to proceed without such a hearing, and the trial of the defendant cannot go forward unless it is properly determined that defendant is competent to stand trial. (See, e.g., Pate v. Robinson, supra, 383 U.S. 375, 384 [15 L.Ed.2d 815, 821]; People v. Marks (1988) 45 Cal.3d 1335, 1340 [248 Cal.Rptr. 874, 756 P.2d 260].)
Contrary to the implicit suggestion of the majority opinion, the fact that a defendant’s competence is not an element of an offense does not mean that it is constitutionally permissible to place the burden of proof of that issue on the defendant rather than on the prosecution.2 There are numerous matters that are not elements of a criminal offense on which the prosecution, rather than the defendant, bears the burden of proof. For example, although the voluntariness or involuntariness of a confession is not an element of a crime, the Constitution requires that the prosecution, rather than the defense, bear the burden of proving voluntariness by a preponderance of the evidence. (Lego v. Twomey (1972) 404 U.S. 477, 489 [30 L.Ed.2d 618, 627-628, 92 S.Ct. 619].)3 Similarly, although the statute of limitations is not an element of a crime, the prosecution, rather than the defense, bears the burden of proving by a preponderance of the evidence that the alleged crime was committed within the applicable limitations period. (See, e.g., People v. Zamora (1976) 18 Cal.3d 538, 565, fns. 26, 27 [134 Cal.Rptr. 784, 557 P.2d 75]. See generally 1 Witkin & Epstein, Cal. Criminal Law (2d ed. 1988) § 372, p. 426.)
Although the Supreme Court has not yet expressly resolved the question whether a state may properly impose the burden of proof on the competen*920cy issue on the defendant rather than on the prosecution, its past rulings on the competency question are inconsistent with a rule placing the burden of proving incompetency on the defendant. As noted above, in Pate v. Robinson, supra, 383 U.S. 375, the court expressly rejected the notion that a defendant whose competency is in question may “waive” the incompetency issue, holding that once a question as to a defendant’s competency to stand trial has arisen, the trial court has a constitutional obligation to ensure that the trial does not go forward until it is properly determined that the defendant is competent to stand trial. (See also Drope v. Missouri, supra, 420 U.S. 162, 181 [43 L.Ed.2d 103, 118-119].) If the competency of the defendant is so vital and fundamental to a fair trial that neither a defendant nor his counsel may waive the point or consent to a trial without a proper determination of the issue, it is clearly impermissible for a state to permit a defendant to be found competent to stand trial simply on the basis of the defendant’s own failure to prove incompetency rather than on the basis of affirmative proof demonstrating that the defendant is competent. (See Pizzi, Competency to Stand Trial in Federal Courts: Conceptual and Constitutional Problems (1977) 45 U.Chi.L.Rev. 21, 57.) As the DiGilio court put it, in light of the Supreme Court’s emphasis of the fundamental importance of a competent defendant to the basic fairness of the entire trial process, “[e]vidence showing competency must be more persuasive than that showing incompetency” before a defendant may properly be found competent to stand trial. (DiGilio, supra, 538 F.2d 972, 988.)
To put the matter in slightly different terms, the challenged California procedure is unconstitutional because it places too great a risk on the defendant of an erroneous determination of competency. As a number of United States Supreme Court decisions explain, procedural rules assigning the burden of proof on particular issues, or establishing the appropriate standard of proof applicable to a given issue, reflect “a societal judgment about how the risk of error should be distributed between the litigants.” (Santosky v. Kramer (1982) 455 U.S. 745, 755 [71 L.Ed.2d 599, 607, 102 S.Ct. 1388]; see, e.g., Addington v. Texas (1979) 441 U.S. 418, 423-425 [60 L.Ed.2d 323, 329-331, 99 S.Ct. 1804]; Mullaney v. Wilbur (1975) 421 U.S. 684, 700-701 [44 L.Ed.2d 508, 514-523, 95 S.Ct. 1881].) In Speiser v. Randall (1958) 357 U.S. 513 [2 L.Ed.2d 1460, 78 S.Ct. 1332], a civil case, the court explained the practical consequences and policy considerations implicit in the assignment of the burden of proof. The Speiser court stated: “In all kinds of litigation it is plain that where the burden of proof lies may be decisive of the outcome. [Citations.] There is always in litigation a margin of error, representing error in factfinding .... Where one party has at stake an interest of transcending value—as a criminal defendant his liberty— this margin of error is reduced as to him by the process ofplacing on the other *921party the burden of producing a sufficiency of proof in the first instance, and of persuading the factfinder at the conclusion of the trial of his guilt beyond a reasonable doubt. Due process commands that no man shall lose his liberty unless the Government has borne the burden of producing the evidence and convincing the factfinder of his guilt.” (357 U.S. at p. 525 [2 L.Ed.2d at pp. 1472-1473], italics added.) In a competency proceeding, the risk of an erroneous determination of competency can be properly contained within permissible constitutional limits only if the prosecution is required to bear the burden of proving, by at least a preponderance of the evidence, that the defendant is competent to stand trial.
In sum, the majority opinion’s reliance on the Leland, supra, 343 U.S. 790, and Rivera, supra, 429 U.S. 877, decisions is totally misplaced. Those cases simply have no bearing on the distinct constitutional problems posed by a state procedure that places the burden of proof in a competency proceeding on the defendant.
In addition to its reliance on Leland, supra, 343 U.S. 790, and Rivera, supra, 429 U.S. 877, the opinion suggests that “sound practical and policy considerations” support a rule placing the burden of proving incompetency on the defendant because the defendant and his counsel can be expected to have better access than the People to the facts relevant to the competency inquiry. (See maj. opn., ante, p. 885.) While the question of access to the facts of incompetency is a relevant consideration which may well justify placing the initial burden of production, i.e., the burden of going forward with evidence, on the defendant, it cannot justify a rule of law placing the burden of proof on the defendant, a rule of law that as just explained permits the trier of fact to find the defendant competent even when the evidence of competence does not outweigh the evidence of incompetence.4 Furthermore, to the extent that the majority’s argument purports to suggest that a rule placing the burden of proving competency on the prosecution is “impractical” in light of the realities of the incompetency inquiry, the opinion’s *922conclusion cannot be squared with the fact that both the federal courts and the great majority of state courts have long operated under a procedure in which the prosecution bears the burden of proof on the competency issue.
Thus, I conclude that the opinion is in error in upholding the constitutionality of Penal Code section 1369, subdivision (f) insofar as the provision establishes a presumption that a defendant is competent to stand trial and places the burden on the defendant to prove his incompetency. I agree with defendant that the trial court committed constitutional error in instructing the jury pursuant to this provision.
Finally, under the facts of this case, the error cannot properly be found harmless under the applicable standard for federal constitutional error. (See, e.g., Chapman v. California (1967) 386 U.S. 18, 24 [17 L.Ed.2d 705, 710-711, 87 S.Ct. 824, 24 A.L.R.3d 1065].) At the competency hearing in this matter, conflicting testimony was introduced as to defendant’s competency to stand trial. Although a number of prosecution experts testified that, in their opinion, defendant was competent to stand trial, the psychiatrist who had the longest relationship with defendant testified that, in his view, defendant was not presently competent to stand trial. In addition, a defense investigator testified as to defendant’s repeated refusal to discuss any substantive aspect of the case with him.
Furthermore, in his closing argument to the jury at the competency phase, the prosecutor made a point of emphasizing that the defendant bore the burden of proving his own incompetency. The prosecutor told the jury in this regard: “So the question is, has the defense proven that this defendant is mentally incompetent to stand trial. It’s the defense burden, [fl] It’s not like the regular criminal case that you have where we have the burden of proving someone guilty beyond a reasonable doubt. We don’t have that burden here, [fl] It’s the defense burden. The law put that burden on the defendant because otherwise you would have every defendant saying— when it’s a tough case against him, every defendant would be coming in and saying, I can’t cooperate with my attorney, I can’t understand the charges. And you wouldn’t have any trials occurring. So the law has made it tough on the defendant to try to prove that.”
Under these circumstances, the constitutional error in instructing the jury that defendant bore the burden of proof on the competency issue cannot be found harmless beyond a reasonable doubt.
*923Accordingly, in light of the prejudicial constitutional error at the competency phase, I conclude that the judgment should be reversed in its entirety. (See, e.g., People v. Marks, supra, 45 Cal.3d 1335; People v. Hale (1988) 44 Cal.3d 531 [244 Cal.Rptr. 114, 749 P.2d 769].)
Appellant’s petition for a rehearing was denied February 14, 1991. Mosk, J., and Broussard, J., were of the opinion that the petition should be granted.
Penal Code section 1369 provides in relevant part: “A trial by court or jury of the question of mental competence shall proceed in the following order:. . . [ft] (f) In a jury trial, the court shall charge the jury, instructing them on all matters of law necessary for the rendering of a verdict. It shall be presumed that the defendant is mentally competent unless it is proved by a preponderance of the evidence that the defendant is mentally incompetent. The verdict of the jury shall be unanimous.”
Pursuant to this provision, the competency jury in the present case was instructed that “[t]he defendant is presumed to be mentally competent and he has the burden of proving by a preponderance of the evidence that he is mentally incompetent as a result of mental disorder or developmental disability.”
Because a defendant’s competency to stand trial is not an element of a criminal offense, most decisions have held that it is constitutionally permissible for a state to require the prosecution to prove competence only by a preponderance of the evidence, rather than beyond a reasonable doubt. (See, e.g., DiGilio, supra, 538 F.2d 972, 988.) Nonetheless, as explained above, the great majority of decisions have held that the prosecution, rather than the defendant, must bear the burden of proof on this matter.
In Twomey, the court stated: “[W]hen a confession challenged as involuntary is sought to be used against a criminal defendant at his trial, he is entitled to a reliable and clear-cut determination that the confession was in fact voluntarily rendered. Thus, the prosecution must prove at least by a preponderance of the evidence that the confession was voluntary.” (Twomey, supra, 404 U.S. 477, 489 [30 L.Ed.2d 618, 627].)
The “model provision” on competency procedures set forth in the American Bar Association Standards for Criminal Justice speaks directly to this point. Standard 7-4.8, subdivision (c) provides in this regard: “At the [competency] hearing ...[][] (i) The party raising the issue of incompetence should have the burden of going forward with the evidence to show incompetence. If the defendant has moved for evaluation then the defense should have the burden of going forward; if the prosecutor or the court on its own motion or on information supplied by the prosecutor has raised the issue, then the prosecutor should have the burden of going forward. []|] (ii) If the court, after hearing the evidence, finds by the greater weight of the evidence that the defendant is competent to stand trial the matter should proceed to trial; if not, the court should proceed to issues of treatment or habilitation to effect competence.” (2 ABA Standards for Criminal Justice, std. 7-4.8 (2d ed. 1986) p. 7.208. See also id., commentary to std. 7-4.8, at pp. 7.213 to 7.215.)