I cannot agree that in a capital case the guilt and special circumstance verdicts can be upheld where there
*545is evidence that one of the jurors was intoxicated during deliberations. No fewer than five jurors expressed concern that Juror M. was intoxicated during deliberations.
The record provides ample support for the conclusion that the trial court committed reversible error by failing to conduct a thorough inquiry into the juror misconduct here. It is, therefore, inappropriate to saddle appellant, who bears no responsibility for the trial court’s failings, with the burden of reassembling his jury panel and demonstrating anew, to another court on habeas corpus, the prejudicial effect of the trial court’s error.
I.
The majority correctly hold that the trial court was remiss in its duty to conduct, sua sponte, an inquiry into Juror M.’s ability to continue as a member of the panel. (Majority opn., ante, at pp. 518-521.) However, the majority find this omission insufficient to warrant reversal because they believe the record does not “establish that juror M. had actually used intoxicants or that her ability to deliberate was affected by them. ” (Id., at p. 521.)
The majority’s conclusion rests on their claim that the record contains only “the foreman’s unsupported assertion” that Juror M. appeared intoxicated, supplemented with hearsay evidence “that four other jurors had expressed concern” along these lines. (Majority opn., ante, at p. 521.) Added to this supposed evidentiary lapse is defense counsel’s “preference that the court conduct no inquiry.” (Id., at p. 521.) The net effect of these considerations prompts my colleagues to affirm the conviction and special circumstance finding and to relegate appellant to raising the claim of jury misconduct in a habeas corpus proceeding “at which [he] would be able to produce evidence of Juror M.’s condition and behavior.” (Id., at p. 522.)
As a preliminary matter, I cannot join in the majority’s unfortunate suggestion that defense counsel’s acquiescence in and encouragement of the trial court’s decision to forego questioning of the jurors frustrated a full and fair inquiry by the trial court. (Id., at p. 521.) However tactically appropriate counsel’s motives might have been, they could not operate as a waiver of appellant’s personal right to a properly constituted and unanimously deliberating panel of jurors. That right was compromised when the trial court failed to conduct a full inquiry into the matter.
Errors which substantially affect the constitutional right of jury trial are not subject to waiver by a failure to object and may not be cured by consent of the accused’s attorney. (See generally, Witkin, Cal. Criminal Procedure (1963) § 764, pp. 736-737; People v. Bruneman (1935) 4 Cal.App.2d 75 *546[40 P.2d 891]; People v. Garcia (1929) 98 Cal.App. 702, 704 [277 P. 747].) For example, the constitutional guaranty has been interpreted to render ineffective counsel’s stipulation to a verdict by 11 jurors after 1 juror has been discharged for good cause. (People v. Ames (1975) 52 Cal.App.3d 389 [124 Cal.Rptr. 894]; People v. Maes (1965) 236 Cal.App.2d 147 [45 Cal.Rptr. 903].)
If counsel’s acquiescence in the trial court’s failure to conduct an appropriate inquiry was tantamount to consenting to an eventual verdict from only 11 competent jurors, such consent was not binding on appellant. A reversal would be required on the ground that appellant’s right to a unanimous jury verdict was violated.
However, one need not engage in such supposition to identify the reversible error in this case. People v. McNeal (1979) 90 Cal.App.3d 830 [153 Cal.Rptr. 706], provides ample reason why the trial court’s failure to conduct a timely inquiry into the alleged juror misconduct was prejudicial error.
In McNeal, the trial court failed to inquire fully into whether there was good cause to excuse a juror. During deliberations, the juror had revealed her realization, arrived at after hearing a defense witness, that she had personal knowledge about the case. When the matter was brought to the trial judge’s attention, he questioned the foreperson and the juror, but preceded each question session with a caveat that he did not want to “go into factual matters.” (90 Cal.App.3d at p. 836.) Ultimately, the judge decided to retain the juror on the panel and instructed the jury to resume deliberations. (Ibid.)
The Court of Appeal held that the failure to conduct a more thorough inquiry violated the accused’s constitutional right to a fair and impartial jury. (Cal. Const., art. I, § 16.) Like the majority here, the court specifically acknowledged the possibility that no misconduct may have occurred and distinguished other cases where “misconduct could be determined from the facts.” (McNeal, supra, 90 Cal.App.3d at pp. 839-840.) “Here, further inquiry might have demonstrated that there was misconduct, or although there was no misconduct, the juror should be discharged because of her personal knowledge, or that there was no misconduct, personal knowledge, or other good cause for discharging the juror.” (Id., at p. 840, italics added.)
However, in marked contrast to the disposition here, and in the face of the availability of a postappeal habeas corpus proceeding, the court reversed the judgment of conviction. “[W]here the fact of a sworn juror’s impartiality comes into question as a result of that juror’s conduct or statements *547during the course of the trial or the deliberations, the failure of the court to make at least a preliminary inquiry into the facts of such impartiality cannot be said to be error harmless beyond a reasonable doubt.” {Ibid.) My colleagues’ wholehearted adherence to McNeal's duty-of-inquiry rule, with their rejection of its reasoning and ultimate holding, is somewhat puzzling.
One line of cases following this court’s decision in People v. Marsden (1970) 2 Cal.3d 118 [84 Cal.Rptr. 156, 465 P.2d 44] provides further support for the proposition that the trial court’s failure to inquire into Juror M.’s condition requires a reversal of the guilt and special circumstance verdicts.
Marsden holds that when an accused moves for a substitution of appointed counsel, the court must provide him with an opportunity to explain the reasons underlying that motion. Failure to do so constitutes reversible error. (Id., at p. 126; accord People v. Lewis (1978) 20 Cal.3d 496 [143 Cal.Rptr. 138, 573 P.2d 40].)
Several Court of Appeal cases have, following Marsden's reasoning, required trial courts not only to afford the accused an opportunity to explain the specific instances of the attorney’s alleged inadequacies, but also to affirmatively inquire on the record into the bases of the accused’s complaints. (People v. Hill (1983) 148 Cal.App.3d 744, 753 [196 Cal.Rptr. 382]; People v. Cruz (1978) 83 Cal.App.3d 308, 316-319 [147 Cal.Rptr. 740]; People v. Molina (1977) 74 Cal.App.3d 544, 548 [141 Cal.Rptr. 533]; People v. Munoz (1974) 41 Cal.App.3d 62, 66 [115 Cal.Rptr. 726]; People v. Groce (1971) 18 Cal.App.3d 292, 296-297 [95 Cal.Rptr. 688]; see People v. Green (1971) 15 Cal.App.3d 524, 527 [93 Cal.Rptr. 84].)1 Many of these decisions have reversed the appellant’s conviction upon finding that the trial court’s inquiry was less than adequate. (People v. Hill, supra, 148 Cal.App.3d at pp. 755-756; People v. Cruz, supra, 83 Cal.App.3d at pp. 318-319, 334; People v. Munoz, supra, 41 Cal.App.3d at p. 67; People v. Groce, supra, 18 Cal.App.3d at p. 297.)
*548Noting the fundamental nature of the right to counsel which the duty-of-inquiry rule seeks to protect, these courts have emphasized the fact that the trial court’s failure to conduct an adequate inquiry rendered intelligent appellate review of the denial of the substitution motion impossible. The courts have frankly acknowledged that the record was less than complete as to counsel’s alleged inadequacies. (See, e.g., People v. Groce, supra, 18 Cal.App.3d at p. 297.) However, each of these courts has refused to speculate as to the nature of the inadequacies and has not required the question to be litigated in collateral proceedings.2 This reasoning is entirely appropriate in the present case.
Additionally, several practical considerations severely undermine the wisdom of requiring appellant to relitigate this matter on habeas corpus. For example, it is highly unlikely that an examination of Juror M.—assuming she can be found at this late date—will produce anything more than a staunch denial as to whether she had consumed intoxicating substances during the period of deliberations.
Here, as in all criminal cases, Juror M. no doubt took an oath to “well and truly try the matter in issue . . . and a true verdict render according to the evidence.” (Code Civ. Proc., § 604; Pen. Code, § 1046; see Keene & George, Cal. Superior Court Criminal Trial Judge’s Benchbook (1984) p. 243.) Like her colleagues, she was instructed that “[b]oth the People and the defendant have a right to expect that [she would] conscientiously consider and weigh the evidence and apply the law of the case . . . . ” (CALJIC No. 1.00 (1979 Rev.).) She was admonished that her “attitude and conduct ... at the beginning of . . . deliberations are matters of considerable importance.” (CALJIC No. 17.41.) And, she was told to “decide the case for [herself], but . . . only after a discussion of the evidence and instructions with the other jurors.” (CALJIC No. 17.40.)
What juror would, in disobedience to these solemn admonitions, admit to drinking alcohol and smoking marijuana during deliberations? Just as “the bias of a juror will rarely be admitted by the juror himself,”3 violations of a juror’s oath and acts in derogation of a court’s clear instructions will not be easily confessed to in proceedings conducted long after the fact. (See McIlwain v. United States (1983) 464 U.S. 972 [78 L.Ed.2d 349, 104 S.Ct. 409] (dis. opn. of Marshall, J. to den. of cert.).)
*549Other problems with the habeas corpus solution are readily apparent. What if Juror M. can be located to testify as to her condition during deliberations, but none of the other jurors who observed her? What if the foreperson, Mrs. Olds, who first brought the matter to the judge’s attention, cannot be located to reaffirm her observations, or none of the other jurors who independently corroborated her account, can be found? Is the trial court to determine the matter without all of the percipient witnesses to the misconduct? In short, if reversible error were committed at the guilt and special circumstances trial, why should the trial court’s failings, for which appellant cannot be held responsible, deprive him of an opportunity to seek the best result which the circumstances permit?
More fundamentally, requiring appellant to resolve the question of prejudice in a habeas corpus proceeding at this late date may unfairly require superhuman recall powers of even the most diligent juror. Assuming the members of the panel in appellant’s case can be located and reassembled, they will be called upon to remember with crystal clarity, over four years after the fact, the behavior and demeanor of one of their colleagues. (Cf. In re Finley (1968) 68 Cal.2d 389, 393 [66 Cal.Rptr. 733, 438 P.2d 381] [holding that it is inappropriate to determine whether an accused’s foreign conviction satisfies the enhanced punishment requirements of the habitual criminal statute (former Pen. Code, § 644, subd. (a)) “on the basis of the testimony of witnesses who may have died or disappeared or whose memories have faded.” (Italics added.)].) Neither logic nor good sense dictates such a procedure, especially when appellant’s eligibility for capital punishment hangs in the balance.
It is also unclear how much additional admissible evidence of the event will be introduced in a habeas corpus proceeding. Certainly one formidable obstacle is Evidence Code section 1150. Subdivision (a) of that statute provides that “[u]pon an inquiry as to the validity of a verdict, any otherwise admissible evidence may be received as to statements made, or conduct, conditions, or events occurring, within or without the jury room, of such a character as is likely to have influenced the verdict improperly. No evidence is admissible to show the effect of such statement, conduct, condition, or event upon a juror either in influencing him to assent to or dissent from the verdict or concerning the mental processes by which it was determined.”
As is well established, ‘“[a] juryman may testify to any facts bearing upon the question of the existence of the disturbing influence, but he cannot be permitted to testify how far that influence operated upon his mind.’” (People v. Stokes (1894) 103 Cal. 193, 197 [37 P. 207].) “The law, in its wisdom, does not allow a juror to purge himself in that way.” (Ibid.) Thus, under Evidence Code section 1150, “proof of overt acts, objectively ascer*550tainable” is permitted, while “proof of the subjective reasoning processes of the individual juror” is not. (People v. Hutchinson (1969) 71 Cal.2d 342, 349 [78 Cal.Rptr. 196, 455 P.2d 132].) “Because the latter can be neither corroborated nor disproved, they are excluded.” (People v. Adame (1973) 36 Cal.App.3d 402, 408, fn. 5 [111 Cal.Rptr. 462].)
Certainly objective evidence of Juror M.’s state during the deliberations will be admissible on the question of her competency to perform her duties. However, no evidence will be permitted as to whether her condition, intoxicated or not, affected her ability to deliberate along with her colleagues, since such evidence would involve proof of her “subjective reasoning processes” prohibited by Evidence Code section 1150. For this reason, it is unlikely that a habeas corpus proceeding will uncover significant facts other than those already in this assertedly “insufficient” appellate record.
On the record before this court, a reversal is compelled. No fewer than five jurors expressed concerns that Juror M. had been intoxicated during deliberations. Three of these jurors indicated to foreperson Olds that they had smelled marijuana on her breath. Unlike the majority, I am unwilling to dismiss these expressions of concern as “hearsay of limited probative value” (majority opn., ante, at p. 521), since they cast severe doubts on Juror M.’s ability to deliberate. Those doubts are substantial enough to render the guilt and special circumstance verdicts suspect.4 To affirm those verdicts and thereby permit appellant to be eligible for the death penalty is to invite violation of the reliability principle that this court and the United States Supreme Court have invoked in capital cases. (See People v. Chadd (1981) 28 Cal.3d 739, 751 [170 Cal.Rptr. 798, 621 P.2d 837]; Lockett v. Ohio (1978) 438 U.S. 586, 604 [57 L.Ed.2d 973, 989, 98 S.Ct. 2954].) For that reason, I cannot agree.
II.
The importance of unanimous juror participation in the deliberative process cannot be overemphasized. Chief Justice Wright aptly expressed this idea a decade ago in People v. Collins (1976) 17 Cal.3d 687 [131 Cal.Rptr. 782, 552 P.2d 742], As he observed, “[t]he requirement that 12 persons reach a unanimous verdict is not met unless those 12 reach their consensus through deliberations which are the common experience of all of them. . . . *551Deliberations provide the jury with the opportunity to review the evidence in light of the perception and memory of each member. Equally important in shaping a member’s viewpoint are the personal reactions and interactions as any individual juror attempts to persuade others to accept his or her viewpoint. . . . The elements of number and unanimity combine to form an essential element of unity in the verdict. By this we mean that a defendant may not be convicted except by 12 jurors who have heard all the evidence and argument and who together have deliberated to unanimity. ” {Id., at p. 693, italics added.)
In addition, ensuring the sanctity of deliberations and the competency of those who engage in them is, particularly in a capital case, fundamental to the constitutional right of trial by jury. “It is vital in capital cases that the jury should pass upon the case free from external causes tending to disturb the exercise of deliberate and unbiassed [¿7c] judgment. Nor can any ground of suspicion that the administration of justice has been interfered with be tolerated.” (Mattox v. United States (1892) 146 U.S. 140, 149 [36 L.Ed. 917, 921, 13 S.Ct. 50]; see People v. Hogan, supra, 31 Cal.3d at p. 848 (lead opn. of Bird, C. J.).) As Justice Marshall recently observed, the “precious right” of trial by jury “is denigrated when a conviction resting upon deliberations tainted by a juror’s gross and debilitating impropriety is allowed to stand.” (Mcllwain v. United States, supra, 464 U.S. at p. 975 [78 L.Ed.2d at p. 350] (dis. opn. of Marshall, J. to den. of cert.).)
These observations are a fitting reminder that this court cannot uphold a jury verdict where the unanimity of deliberations and the competency of a juror have been rendered suspect by evidence that the juror was intoxicated. Since the trial court failed to conduct an inquiry into Juror M.’s conduct at a time when that inquiry would have resolved any doubts as to her condition, a reversal of the guilt and special circumstance verdicts is required.
III.
There is one additional point—not discussed by the parties—which raises a question in my mind as to the validity of the felony-murder special circumstance finding. I briefly note the source of my concern.
As the majority point out {ante, p. 536-537), the jury in this case returned a “special verdict” indicating that the murder was committed with express malice aforethought and with deliberation and premeditation. If the jury had been informed that these factors—express malice, premeditation and deliberation—were necessary prerequisites to a determination that the felony-murder special circumstance was true, and if defendant was aware from the *552outset that the jury was to be so instructed, the special verdict would obviously eliminate any issue under Carlos v. Superior Court (1983) 35 Cal.3d 131 [197 Cal.Rptr. 79, 672 P.2d 862],
One potential problem, however, is that the jury in this case was not instructed that any one of these additional factors—express malice, premeditation or deliberation—was a required element of the special circumstance finding. Instead, the court simply told the jury that if it found the special circumstance to be true—applying the erroneous pre- Carlos standard—it should then make an additional and separate finding with respect to express malice, etc.5 The court never informed the jury that if it found that express malice had not been established, it should vacate or alter its special circumstance finding. Thus, the jury apparently never knew the significance of its special “express malice” finding or for what purpose it was being asked to make such a finding.
A further problem is raised by the fact that—at least as far as I have been able to discover—the record does not make it clear when defendant first *553learned that the trial court was going to elicit this special verdict from the jury. The record does indicate that, in the middle of the presentation of the defense case, the prosecution submitted the instruction for a special finding on express malice, etc., which the trial court eventually gave.
However, I cannot tell what precipitated this submission by the prosecution or whether appellant had sufficient notice of the trial court’s decision to elicit this finding to permit him to present his defense with this matter in mind. If appellant formulated and presented his defense with the understanding that intent to kill was irrelevant to the special circumstance finding and his eligibility for the death penalty, I do not believe that the fact that the trial court belatedly decided to obtain an additional “special finding” on express malice would necessarily cure the Carlos problem.
As noted at the outset, the parties have not raised or discussed these questions in their briefs. It may well be that there is material in or outside the record of which I am unaware which demonstrates that my uneasiness on these points is unwarranted.
Appellant’s petition for a rehearing was denied May 22, 1986.
As explained in People v. Munoz, supra, 41 Cal.App.3d at page 66: “[T]he mandate of [Marsden] is not limited necessarily to a case where the trial judge refiises to give the defendant the opportunity to be heard .... [T]he ratio decidendi of the high court’s opinion tells us that the judge’s obligation to listen to an indigent defendant’s reasons for claiming inadequate representation by court-appointed counsel is not a pro forma function. It tells us also that under some circumstances a court’s ruling denying the request for a substitution of attorneys without a careful inquiry into the defendant’s reasons for requesting the substitution ‘is lacking in all the attributes of a judicial determination.’ [Citations.]” This duty-of-inquiry includes “an inquiry into the state of mind of the court-appointed attorney” and an attempt “to ascertain in what particulars the attorney was not providing appellant with a competent defense.” (Ibid.) Munoz has been cited with approval by this court in People v. Lewis, supra, 20 Cal.3d at page 499.
Groce is particularly instructive on this point. The dissent criticized the majority for reversing the conviction without a showing that had counsel not committed the asserted error counsel’s inadequacies were in fact prejudicial to the appellant. (Jd., at pp. 297-298 (dis. opn.).)
McDonough Power Equipment, Inc. v. Greenwood (1984) 464 U.S. 548, 558 [78 L.Ed.2d 663, 672, 104 S.Ct. 845] (conc. opn. of Brennan, J.). See also People v. Diaz (1984) 152 Cal.App.3d 926, 938-939 [200 Cal.Rptr. 77],
These suspicions were in no way cured by the trial court’s admonition to the panel not to consume any intoxicants which “might interfere with [the jurors’] hours [sic] of concentration, their reasoning abilities . . . .” By the time the court gave that cautionary instruction, the jurors had already deliberated some 12 hours, over 75 percent of the total deliberations period. (See People v. Hogan (1982) 31 Cal.3d 815, 847 [183 Cal.Rptr. 817, 647 P.2d 93] (lead opn. of Bird, C. J.).)
In instructing the jury on the elements of the special circumstance, the court stated: “To find that special circumstance, referred to in these instructions as murder in the commission of a robbery, is true, it must be proved that the murder was committed while the defendant was engaged in the commission of a robbery or that the murder was committed during the immediate flight after the commission of a robbery by the defendant and that the murder was committed in order to carry out or advance the commission of the crime of robbery or to facilitate the escape therefrom or to avoid detection.”
Thereafter, in explaining the verdict forms that the jury was being given, the court stated:
“You are instructed that if you find the defendant guilty of murder of the first degree as charged under Count 1 of the Amended Information, then you shall also make a finding in one of the following forms as to whether the murder was committed while the defendant was engaged in the commission of the crime of robbery in violation of Section 211 of the Penal Code, and the finding would be one of the following: [K] We the jury in the above-entitled action find that the murder of William Arias charged under Count 1 of the Amended Information was committed while the defendant was engaged in the commission of a robbery in violation of Section 211 as alleged in the allegation of special circumstance, or; [f¡ We the jury in the above-entitled action find that the murder of William Arias charged under Count 1 of the Amended Information was committed while the defendant was not engaged in the commission of a robbery.
“You are instructed that if you find the defendant Michael Ray Burgener guilty of murder in the first degree committed while engaged in the commission of the crime of robbery within the meaning of Penal Code . . . Section 190.2(a)( 17) (i), then you shall also make a finding in one of the following forms as to whether the murder was committed with express malice aforethought and with deliberation and premeditation: [H] We the jury in the above-entitled action find the murder of William Arias, charged under Count 1 of the Amended Information, was committed with express malice aforethought and with deliberation and premeditation, or; [1f] We the jury in the above-entitled action find that the murder of William Arias charged under Count 1 of the Amended Information was not committed with express malice aforethought and with deliberation and premeditation.
“And those two findings will be submitted to you in the form of special verdict forms.”
The jury thereafter returned two separate verdicts, one finding that defendant had committed the murder during the commission of a robbery as alleged in the special circumstance allegation, and the other finding that the murder was committed with express malice aforethought and with deliberation and premeditation.