with whom
Justice Brennan, Justice Blackmun, and Justice Stevens join, concurring in part and dissenting in part.Every criminal defendant has a constitutional right to be tried by competent jurors. This Court has long recognized that “[d]ue process implies a tribunal both impartial and mentally competent to afford a hearing,” Jordan v. Massachusetts, 225 U. S. 167, 176 (1912), “a jury capable and willing to decide the case solely on the evidence before it.” Smith v. Phillips, 455 U. S. 209, 217 (1982). If, as is charged, members of petitioners’ jury were intoxicated as a result of their use of drugs and alcohol to the point of sleeping through material portions of the trial, the verdict in this case must be set aside. In directing district courts to ignore sworn allegations that jurors engaged in gross and debilitating misconduct, this Court denigrates the precious right to a competent jury. Accordingly, I dissent from that part of the Court’s opinion.1
I
At the outset, it should be noted that petitioners have not asked this Court to decide whether there is sufficient evidence to impeach the jury’s verdict. The question before us is only whether an evidentiary hearing is required to explore *135allegations of juror misconduct and incompetency. As the author of today’s opinion for the Court has noted:
“A hearing permits counsel to probe the juror’s memory, his reasons for acting as he did, and his understanding of the consequences of his actions. A hearing also permits the trial judge to observe the juror’s demeanor under cross-examination and to evaluate his answers in light of the particular circumstances of the case.” Smith v. Phillips, supra, at 222 (O’Connor, J., concurring).2
The allegations of juror misconduct in this case are profoundly disturbing. A few weeks after the verdict was returned, one of the jurors, Vera Asbel, contacted defense counsel and told him she had something she wanted to get off her conscience. App. 247. She stated that at the trial some of the male jurors were drinking every day and then “slept through the afternoons.” Ibid. According to Asbel, another juror, Tina Franklin, could confirm these charges. Ibid. Despite these revelations, the District Court refused to hold an evidentiary hearing. Like this Court, the District Judge believed that Asbel’s statements to defense counsel were inadmissible under Rule 606(b). Id., at 181-182.
Several months later, Asbel’s allegations were buttressed by a detailed report of rampant drug and alcohol abuse by jury members, volunteered by another juror, Daniel Hardy.3 In a sworn statement, Hardy indicated that seven members *136of the jury, including himself, regularly consumed alcohol during the noon recess. App. 210. He reported that four male jurors shared up to three pitchers of beer on a daily basis. Id., at 212. Hardy himself “consumed alcohol all the time.” Id., at 239. The female juror selected as foreperson was described as “an alcoholic” who would drink a liter of wine at lunch. Id., at 213-214. Two other female jurors regularly consumed one or two mixed drinks at lunch. Id., at 215.
The four male jurors did not limit themselves to alcohol, however. They smoked marijuana “[j]ust about every day.” Id., at 222. In addition, two of them ingested “a couple lines” of cocaine on several occasions. Id., at 225. At times two of the jurors used all three substances — alcohol, cocaine, and marijuana. Id., at 229. Hardy also maintained that the principal drug user, identified as “John,” used cocaine during breaks in the trial. Id., at 234. “I knew he had that little contraption and he was going to the bathroom and come back down sniffing . . . like he got... a cold.” Id., at 234-235. Hardy’s statement supported Asbel’s assessment of the impact of alcohol and drug consumption; he noted that “[m]ost, some of the jurors,” were “falling asleep all the time during the trial.” Id., at 229. At least as to John, the effects of drugs and alcohol went beyond inability to stay awake at trial: “John just talked about how he was flying,” which Hardy understood to mean that “he was messed up.” Ibid. Hardy admitted that on one day during the trial his reasoning ability was affected by his use of alcohol and marijuana. Id., at 239. These allegations suggest that several of the jurors’ senses were significantly dulled and distorted by drugs and alcohol.4 In view of these charges, Hardy’s characteriza*137tion of the jury as “one big party,” id., at 209, is quite an understatement.
II
Despite the seriousness of the charges, the Court refuses to allow petitioners an opportunity to vindicate their fundamental right to a competent jury. The Court holds that petitioners are absolutely barred from exploring allegations of juror misconduct and incompetency through the only means available to them — examination of the jurors who have already voluntarily come forward. The basis for the Court’s ruling is the mistaken belief that juror testimony concerning drug and alcohol abuse at trial is inadmissible under Federal Rule of Evidence 606(b) and is contrary to the policies the Rule was intended to advance.
I readily acknowledge the important policy considerations supporting the common-law rule against admission of jury testimony to impeach a verdict, now embodied in Federal Rule of Evidence 606(b): freedom of deliberation, finality of verdicts, and protection of jurors against harassment by dissatisfied litigants. See, e. g., McDonald v. Pless, 238 U. S. 264, 267-268 (1915); Advisory Committee’s Notes on Fed. Rule Evid. 606(b), 28 U. S. C. App., p. 700. It has been simultaneously recognized, however, that “simply putting verdicts beyond effective reach can only promote irregularity and injustice.” Ibid. If the above-referenced policy considerations seriously threaten the constitutional right to trial by a fair and impartial jury, they must give way. See Parker v. Gladden, 385 U. S. 363 (1966); Mattox v. United States, 146 U. S. 140 (1892).
In this case, however, we are not faced with a conflict between the policy considerations underlying Rule 606(b) and petitioners’ Sixth Amendment rights. Rule 606(b) is not ap*138plicable to juror testimony on matters unrelated to the jury’s deliberations. By its terms, Rule 606(b) renders jurors incompetent to testify only as to three subjects: (i) any “matter or statement” occurring during deliberations; (ii) the “effect” of anything upon the “mind or emotions” of any juror as it relates to his or her “assent to or dissent from the verdict”; and (iii) the “mental processes” of the juror in connection with his “assent to or dissent from the verdict.”5 Even as to matters involving deliberations, the bar is not absolute.6
It is undisputed that Rule 606(b) does not exclude juror testimony as to matters occurring before or after deliberations. See 3 D. Louisell & C. Mueller, Federal Evidence § 290, p. 151 (1979); cf. Note, Impeachment of Verdicts by Jurors—Rule of Evidence 606(b), 4 Wm. Mitchell L. Rev. 417, 431, n. 88 (1978). But, more particularly, the Rule only “operates to prohibit testimony as to certain conduct by the jurors which has no verifiable manifestations,” 3 J. Weinstein & M. Berger, Weinstein’s Evidence ¶ 606[04], p. 606-28 (1985) (emphasis added); as to other matters, jurors remain competent to testify. See Fed. Rule Evid. 601. Because petitioners’ claim of juror misconduct and incompetency involves objectively verifiable conduct occurring prior to deliberations, juror testimony in support of the claims is admissible under Rule 606(b).
*139The Court’s analysis of legislative history confirms the inapplicability of Rule 606(b) to the type of misconduct alleged in this case. As the Court emphasizes, the debate over two proposed versions of the Rule — the more restrictive Senate version ultimately adopted and the permissive House version, reproduced ante, at 123, n., focused on the extent to which jurors would be permitted to testify as to what transpired during the course of the deliberations themselves.7 Similarly, the Conference Committee Report, quoted by the Court, ante, at 125, compares the two versions solely in terms of the admissibility of testimony as to matters occurring during, or relating to, the jury’s deliberations: “[T]he House bill allows a juror to testify about objective matters occurring during the jury’s deliberation, such as the misconduct of another juror or the reaching of a quotient verdict. The Senate bill does not permit juror testimony about any matter or statement occurring during the course of the jury’s deliberations.” H. R. Conf. Rep. No. 93-1597, p. 8 (1974) (emphasis added). The obvious conclusion, and the one compelled by Rule 601, is that both versions of Rule 606(b) would have permitted jurors to testify as to matters not involving deliberations. The House Report’s passing reference to *140juror intoxication during deliberations, quoted ante, at 122-123, is not to the contrary. Reflecting Congress’ consistent focus on the deliberative process, it suggests only that the authors of the House Report believed that the Senate version of Rule 606(b) did not allow testimony as to juror intoxication during deliberations.8
In this case, no invasion of the jury deliberations is contemplated. Permitting a limited postverdict inquiry into juror consumption of alcohol and drugs during trial would not “make what was intended to be a private deliberation, the constant subject of public investigation — to the destruction of all frankness and freedom of discussion and conference.” McDonald v. Pless, 238 U. S., at 267-268. “Allowing [jurors] to testify as to matters other than their own inner reactions involves no particular hazard to the values sought to be protected.” Advisory Committee’s Notes on Fed. Rule Evid. 606(b), 28 U. S. C. App., p. 701.
Even if I agreed with the Court’s expansive construction of Rule 606(b), I would nonetheless find the testimony of juror intoxication admissible under the Rule’s “outside influence” exception.9 As a common-sense matter, drugs and *141alcohol are outside influences on jury members. Commentators have suggested that testimony as to drug and alcohol abuse, even during deliberations, falls within this exception. “[T]he present exception paves the way for proof by the affidavit or testimony of a juror that one or more jurors became intoxicated during deliberations. ... Of course the use of hallucinogenic or narcotic drugs during deliberations should similarly be provable.” 3 Louisell & Mueller, Federal Evidence, § 289, pp. 143-145 (footnote omitted). See 3 Weinstein & Berger, Weinstein’s Evidence, supra, ¶ 606[04], pp. 606-29 — 606-32 (“Rule 606(b) would not render a witness incompetent to testify to juror irregularities such as intoxication . . . regardless of whether the jury misconduct occurred within or without the jury room”). The Court suggests that, if these are outside influences, “a virus, poorly prepared food, or a lack of sleep” would also qualify. Ante, at 122. Distinguishing between a virus, for example, and a narcotic drug is a matter of line-drawing. Courts are asked to make these sorts of distinctions in numerous contexts; I have no doubt they would be capable of differentiating between the intoxicants involved in this case and minor indispositions not affecting juror competency.
The Court assures us that petitioners’ Sixth Amendment interests are adequately protected by other aspects of the trial process: voir dire; observation during trial by the court, counsel, and courtroom personnel; and observation by fellow jurors (so long as they report inappropriate juror behavior to the court before a verdict is rendered). Ante, at 127. Reliance on these safeguards, to the exclusion of an evi*142dentiary hearing, is misguided. Voir dire cannot disclose whether a juror will choose to abuse drugs and alcohol during the trial. Moreover, the type of misconduct alleged here is not readily verifiable through nonjuror testimony. The jurors were not supervised by courtroom personnel during the noon recess, when they consumed alcoholic beverages and used drugs. Hardy reported that he and his three companions purposely avoided observation. They smoked marijuana and used cocaine first in a municipal parking garage and later “[d]own past the Hyatt Regency” because it was “away from everybody.” App. 218, 222.
Finally, any reliance on observations of the court is particularly inappropriate on the facts of this case. The District Judge maintained that he had a view of the jury during the trial, and “[y]ou might infer . . . that if I had seen somebody sleeping I would have done something about that.” Id., at 167. However, as the portions of the trial transcript quoted ante, at 113-114, indicate, the judge had abdicated any responsibility for monitoring the jury. He stated: “I’m going to — not going to take on that responsibility” and “I’m not going to sit here and watch. I’m — among other things, I’m not going to see — . ...” Tr. 12-100—12-101.
HH HH I — I
The Court acknowledges that postverdict investigation into juror misconduct would in some instances lead to the invalidation of verdicts reached after irresponsible or improper juror behavior,” but maintains that “[i]t is not at all clear . . . that the jury system could survive such efforts to perfect it.” Ante, at 120. Petitioners are not asking for a perfect jury. They are seeking to determine whether the jury that heard their case behaved in a manner consonant with the minimum requirements of the Sixth Amendment. If we deny them this opportunity, the jury system may survive, but the constitutional guarantee on which it is based will become meaningless.
I dissent.
I agree with the Court’s disposition of petitioners’ convictions under 18 U. S. C. §§ 371 and 1341. Thus, I join Parts III and IV of the Court’s opinion.
See also Remmer v. United States, 347 U. S. 227, 229-230 (1954); Sullivan v. Fogg, 613 F. 2d 465, 467-468 (CA2 1980).
Both Asbel and Hardy contacted defense counsel on their own initiative. Asbel telephoned, see App. 246-247, while Hardy simply showed up at counsel’s home and stated: “I had some things on my mind that had been bothering me a long time and I wanted to clear my conscience.” Id., at 209. In addition, the District Judge reported that the jury foreperson had contacted his office. “She wanted to know when there was going to be a hearing and she wanted to testify.” Id., at 172. This is not a case where jury members were being pursued and harassed by losing litigants. Thus, the concerns underlying the local rule cited by the Court, ante, at 126, are not implicated in this case.
The Court’s attempt to downplay the seriousness of the charges of incompetence is unconvincing: “The only allegations concerning the jurors’ ability to properly consider the evidence were Hardy’s observations that some jurors were ‘falling asleep all the time during the trial,’ and that Hardy’s own reasoning ability was affected on one day of the trial.” Ante, at 126. Even if this were the extent of the incompetence alleged, the *137claim that several jurors were “falling asleep all the time during the trial” and that one had impaired mental faculties raises a serious question of juror incompetence. If only one juror were shown to be incompetent, the verdict could not stand. Cf. Parker v. Gladden, 385 U. S. 363, 365-366 (1966).
Rule 606(b) provides, in relevant part:
“[A] juror may not testify as to any matter or statement occurring during the course of the jury’s deliberations or to the effect of anything upon his or any other juror’s mind or emotions as influencing him to assent to or dissent from the verdict or indictment or concerning his mental processes in connection therewith, except that a juror may testify on the question whether extraneous prejudicial information was improperly brought to the jury’s attention or whether any outside influence was improperly brought to bear upon any juror.”
Rule 606(b) expressly authorizes jurors to testify as to “extraneous prejudicial information” or “outside influence.” See infra, at 140, and n. 9.
Proponents of the more restrictive Senate version were reluctant to allow juror testimony as to irregularities in the process by which a verdict was reached, such as the resort to a “quotient verdict.” See, e. g., 120 Cong. Rec. 2374-2375 (1974) (statement of Rep. Wiggins); 117 Cong. Rec. 33642, 33645 (1971) (letter from Sen. McClellan); id., at 33649, 33655 (Dept. of Justice Analysis and Recommendations Regarding Revised Draft of Proposed Rules of Evidence for the U. S. Courts and Magistrates).
As the Court explains, ante, at 124, the Senate rejected the House version because it “would have the effect of opening verdicts up to challenge on the basis of what happened during the jury’s internal deliberations, for example, where a juror alleged that the jury refused to follow the trial judge’s instructions or that some of the jurors did not take part in deliberations.” S. Rep. No. 93-1277, p. 13 (1974) (emphasis added). See also id., at 14 (“[R]ule 606 should not permit any inquiry into the internal deliberations of the jurors”).
H. R. Rep. No. 93-650, p. 10 (1973) (“Under this formulation a quotient verdict could not be attacked through the testimony of a juror, nor could a juror testify to the drunken condition of a fellow juror which so disabled him that he could not participate in the jury’s deliberations”).
The sole support for the Court’s cramped interpretation of this exception is the isolated reference to juror intoxication at deliberations, contained in the House Report, quoted supra, n. 8. The source for the reference is a letter to the House Subcommittee, to the effect that the version of the Rule adopted by the Senate would not allow inquiry into juror consumption of alcohol during deliberations. The letter was offered in support of reinstatement of the original form of the Rule (the version adopted by the House); the letter focused primarily on the question whether inquiry into quotient verdicts should be permitted. See Rules of Evidence, Hearings before the Special Subcommittee on Reform of Federal Criminal Laws of the House Committee on the Judiciary, 93d Cong., 1st Sess., 389 (1973). In a subsequent letter, the writer dropped any reference to the question of intoxication, focusing exclusively on the issue of *141quotient verdicts. See Rules of Evidence (Supplement), Hearings before the Subcommittee on Criminal Justice of the House Committee on the Judiciary, 93d Cong., 1st Sess., 27-28 (1973). Moreover, this reference is hardly dispositive. The comparison was provided to show that the House version was “the better practice.” H. R. Rep. No. 93-650, supra, at 10. None of the subsequent Committee Reports make any allusion to juror intoxication.