(2) Exceptions. A juror may testify about whether:
(A) extraneous prejudicial information was improperly brought to the jury’s attention;
(B) an outside influence was improperly brought to bear on any juror; or
(C) a mistake was made in entering the verdict on the verdict form.
Nor may the juror's affidavit or evidence of any statement by the juror indicating an effect of this kind be received.
TANNER v. U.S. 483 U.S. 107, 107 S.Ct. 2739 (1987)
Petitioners William Conover and Anthony Tanner were convicted of conspiring to defraud the United States in violation of 18 U.S.C. s 371, and of committing mail fraud...
The day before petitioners were scheduled to be sentenced, Tanner filed a motion [which included an] affidavit [from] Tanner's attorney [describing] an unsolicited telephone call from one of the trial jurors [who alleged] that several of the jurors consumed alcohol during the lunch breaks at various times throughout the trial, causing them to sleep through the afternoons....The District Court concluded that juror testimony on intoxication was inadmissible under Federal Rule of Evidence 606(b) to impeach the jury's verdict. The District Court invited petitioners to call any nonjuror witnesses, such as courtroom personnel, in support of the motion for new trial. Tanner's counsel ... testified that he had observed one of the jurors “in a sort of giggly mood” [and] the judge referred to a[n earlier] conversation between defense counsel and the judge during the trial on the possibility that jurors were sometimes falling asleep.
* * *
In another affidavit, Tanner's attorney stated that he received an unsolicited visit at his residence from a second juror [who] ... stated that he “felt like ... the jury was on one big party.” [The juror] indicated that seven of the jurors drank alcohol during the noon recess. Four jurors ... consumed between them “a pitcher to three pitchers” of beer during various recesses.... Of the three other jurors who were alleged to have consumed alcohol, ... on several occasions he observed two jurors having one or two mixed drinks during the lunch recess, and one other juror, who was also the foreperson, having a liter of wine on each of three occasions. [The juror] also stated that he and three other jurors smoked marijuana quite regularly during the trial.... Moreover, ... he observed one juror ingest cocaine five times and another juror ingest cocaine two or three times. One juror sold a quarter pound of marijuana to another juror during the trial, and took marijuana, cocaine, and drug paraphernalia into the courthouse. [The juror] noted that some of the jurors were falling asleep during the trial, and that one of the jurors described himself ... as “flying.”
The District Court ... denied petitioners' motion for a new trial.... The Court of Appeals for the Eleventh Circuit affirmed.... We granted certiorari to consider whether the District Court was required to hold an evidentiary hearing, including juror testimony, on juror alcohol and drug use during the trial, and to consider [other evidentiary issues]. ... Petitioners assert that... juror testimony on ingestion of drugs or alcohol during the trial is not barred by Federal Rule of Evidence 606(b). Moreover, petitioners argue that whether or not authorized by Rule 606(b), an evidentiary hearing including juror testimony on drug and alcohol use is compelled by their Sixth Amendment right to trial by a competent jury.
By the beginning of this century, if not earlier, the near‑universal and firmly established common‑law rule in the United States flatly prohibited the admission of juror testimony to impeach a jury verdict....
Exceptions to the common‑law rule were recognized only in situations in which an “extraneous influence,” Mattox v. United States, 146 U.S. 140, 149 (1892), was alleged to have affected the jury. In Mattox, this Court held admissible the testimony of jurors describing how they heard and read prejudicial information not admitted into evidence. The Court allowed juror testimony on influence by outsiders in Parker v. Gladden, 385 U.S. 363, 365 (1966) (bailiff's comments on defendant), and Remmer v. United States, 347 U.S. 227, 228‑230 (1954) (bribe offered to juror). See also Smith v. Phillips, 455 U.S. 209 (1982) (juror in criminal trial had submitted an application for employment at the District Attorney's office). In situations that did not fall into this exception for external influence, however, the Court adhered to the common‑law rule against admitting juror testimony to impeach a verdict. McDonald v. Pless, 238 U.S. 264 (1915); Hyde v. United States, 225 U.S. 347, 384 (1912).
Lower courts used this external/internal distinction to identify those instances in which juror testimony impeaching a verdict would be admissible. The distinction was not based on whether the juror was literally inside or outside the jury room when the alleged irregularity took place; rather, the distinction was based on the nature of the allegation. Clearly a rigid distinction based only on whether the event took place inside or outside the jury room would have been quite unhelpful. For example, under a distinction based on location a juror could not testify concerning a newspaper read inside the jury room. Instead, of course, this has been considered an external influence about which juror testimony is admissible.... Similarly, under a rigid locational distinction jurors could be regularly required to testify after the verdict as to whether they heard and comprehended the judge's instructions, since the charge to the jury takes place outside the jury room. Courts wisely have treated allegations of a juror's inability to hear or comprehend at trial as an internal matter....
Most significant for the present case, however, is the fact that lower federal courts treated allegations of the physical or mental incompetence of a juror as “internal” rather than “external” matters. In United States v. Dioguardi, 492 F.2d 70 (CA2 1974), the defendant Dioguardi received a letter from one of the jurors soon after the trial in which the juror explained that she had “eyes and ears that ... see things before [they] happen,” but that her eyes “are only partly open” because “a curse was put upon them some years ago.” Armed with this letter and the opinions of seven psychiatrists that the letter suggested that the juror was suffering from a psychological disorder, Dioguardi sought a new trial or in the alternative an evidentiary hearing on the juror's competence. The District Court denied the motion and the Court of Appeals affirmed. The Court of Appeals noted “[t]he strong policy against any post‑verdict inquiry into a juror's state of mind,” id., at 79, and observed:
“The quickness with which jury findings will be set aside when there is proof of tampering or external influence, ... parallel the reluctance of courts to inquire into jury deliberations when a verdict is valid on its face.... Such exceptions support rather than undermine the rationale of the rule that possible internal abnormalities in a jury will not be inquired into except 'in the gravest and most important cases.'
Substantial policy considerations support the common‑law rule against the admission of jury testimony to impeach a verdict. As early as 1915 this Court explained the necessity of shielding jury deliberations from public scrutiny:
“[L]et it once be established that verdicts solemnly made and publicly returned into court can be attacked and set aside on the testimony of those who took part in their publication and all verdicts could be, and many would be, followed by an inquiry in the hope of discovering something which might invalidate the finding. Jurors would be harassed and beset by the defeated party in an effort to secure from them evidence of facts which might establish misconduct sufficient to set aside a verdict. If evidence thus secured could be thus used, the result would be to 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... There is little doubt that postverdict investigation into juror misconduct would in some instances lead to the invalidation of verdicts reached after irresponsible or improper juror behavior. It is not at all clear, however, that the jury system could survive such efforts to perfect it.Allegations of juror misconduct, incompetency, or inattentiveness, raised for the first time days, weeks, or months after the verdict, seriously disrupt the finality of the process.... Moreover, full and frank discussion in the jury room, jurors' willingness to return an unpopular verdict, and the community's trust in a system that relies on the decisions of laypeople would all be undermined by a barrage of postverdict scrutiny of juror conduct. Federal Rule of Evidence 606(b) is grounded in the common‑law rule against admission of jury testimony to impeach a verdict and the exception for juror testimony relating to extraneous influences....
[P]etitioners argue that substance abuse constitutes an improper “outside influence” about which jurors may testify under Rule 606(b). In our view the language of the Rule cannot easily be stretched to cover this circumstance. However severe their effect and improper their use, drugs or alcohol voluntarily ingested by a juror seems no more an “outside influence” than a virus, poorly prepared food, or a lack of sleep.
In any case, whatever ambiguity might linger in the language of Rule 606(b) as applied to juror intoxication is resolved by the legislative history of the Rule. * * *
[The] legislative history demonstrates with uncommon clarity that Congress specifically understood, considered, and rejected a version of Rule 606(b) that would have allowed jurors to testify on juror conduct during deliberations, including juror intoxication. This legislative history provides strong support for the most reasonable reading of the language of Rule 606(b)‑‑ that juror intoxication is not an “outside influence” about which jurors may testify to impeach their verdict.
Finally, even if Rule 606(b) is interpreted to retain the common‑law exception allowing postverdict inquiry of juror incompetence in cases of “substantial if not wholly conclusive evidence of incompetency,” Dioguardi, 492 F.2d, at 80, the showing made by petitioners falls far short of this standard. The affidavits and testimony presented in support of the first new trial motion suggested, at worst, that several of the jurors fell asleep at times during the afternoons. The District Court Judge appropriately considered the fact that he had “an unobstructed view” of the jury, and did not see any juror sleeping.... The juror affidavit submitted in support of the second new trial motion was obtained in clear violation of the District Court's order and the court's local rule against juror interviews, MD Fla.Rule 2.04(c); on this basis alone the District Court would have been acting within its discretion in disregarding the affidavit. In any case, although the affidavit of juror Hardy describes more dramatic instances of misconduct, Hardy's allegations of incompetence are meager. Hardy stated that the alcohol consumption he engaged in with three other jurors did not leave any of them intoxicated. App. to Pet. for Cert. 47 (“I told [the prosecutor] that we would just go out and get us a pitcher of beer and drink it, but as far as us being drunk, no we wasn't”). 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 his own reasoning ability was affected on one day of the trial. App. to Pet. for Cert. 46, 55. These allegations would not suffice to bring this case under the common‑law exception allowing post‑verdict inquiry when an extremely strong showing of incompetency has been made.
Petitioners also argue that the refusal to hold an additional evidentiary hearing at which jurors would testify as to their conduct “violates the sixth amendment's guarantee to a fair trial before an impartial and competent jury.” (emphasis in original).
This Court has recognized that a defendant has a right to “a tribunal both impartial and mentally competent to afford a hearing. In this case the District Court held an evidentiary hearing in response to petitioners' first new trial motion at which the judge invited petitioners to introduce any admissible evidence in support of their allegations. At issue in this case is whether the Constitution compelled the District Court to hold an additional evidentiary hearing including one particular kind of evidence inadmissible under the Federal Rules.
As described above, long‑recognized and very substantial concerns support the protection of jury deliberations from intrusive inquiry. Petitioners' Sixth Amendment interests in an unimpaired jury, on the other hand, are protected by several aspects of the trial process. The suitability of an individual for the responsibility of jury service, of course, is examined during voir dire. Moreover, during the trial the jury is observable by the court, by counsel, and by court personnel. See United States v. Provenzano, 620 F.2d 985, 996‑997 (CA3 1980) (marshal discovered sequestered juror smoking marijuana during early morning hours). Moreover, jurors are observable by each other, and may report inappropriate juror behavior to the court before they render a verdict. See Lee v. United States, 454 A.2d 770 (DC App.1982), ... (on second day of deliberations, jurors sent judge a note suggesting that foreperson was incapacitated). Finally, after the trial a party may seek to impeach the verdict by nonjuror evidence of misconduct. See United States v. Taliaferro, 558 F.2d 724, 725‑726 (CA4 1977) (court considered records of club where jurors dined, and testimony of marshal who accompanied jurors, to determine whether jurors were intoxicated during deliberations). Indeed, in this case the District Court held an evidentiary hearing giving petitioners ample opportunity to produce nonjuror evidence supporting their allegations.
In light of these other sources of protection of petitioners' right to a competent jury, we conclude that the District Court did not err in deciding, based on the inadmissibility of juror testimony and the clear insufficiency of the nonjuror evidence offered by petitioners, that an additional post‑verdict evidentiary hearing was unnecessary.... [Omitted is the dissent of four Justices]