Common wisdom is that a jury's verdict cannot later be impeached through the testimony of deliberating jurors regarding misconduct which occurred inside the jury room. Federal Rule of Evidence 606(b) explicitly provides that fellow-juror testimony is inadmissible to impeach a verdict, except to show clerical error on the verdict sheet or the influence of outside or extraneous information. Typical of the latter scenarios is one juror sharing a newspaper story about the case or introducing into deliberations her or his personal research into the scene of a crime or the background of a defendant. Irregularities in the internal deliberations of a jury are generally not proper grounds for subsequent inquiry, for fear of impinging on the free-ranging nature and mysterious ways of the jury process. For example, racial comments among jurors have been found by most courts to be barred from subsequent inquiry under the terms of Rule 606(b).

Yet, a small number of cases have carved out a common law corollary to Rule 606(b), permitting juror testimony to explore whether, despite the strictures of the Rule, due process and Sixth Amendment violations have occurred within the jury. Cases such as Shillcutt v. Gagnon, 827 F.2d 1155 (7th Cir. 1987) have sanctioned inquiry in instances where an "extremely rare abuse," such as pervasive racial prejudice, animated the deliberations. Other courts have been less willing to part the jury curtain. United States v. Benally, 546 F.3d 1230 (10th Cir. 2008) (district court abused discretion in admitting evidence of racial comments in the jury room; it is "not necessarily in the interest of overall justice" to cure expressions of racial prejudice among jury members).

The First Circuit has thrown its lot in with those courts of appeal which have concluded that racial animus toward a defendant is sufficiently destructive of that person's constitutional rights to permit, if not compel, post-verdict inquiry. United States v. Villar, 586 F.3d 76 (1st Cir. 2009). Villar is Hispanic, and after his bank robbery conviction a juror emailed the defense attorney to complain of several fellow jurors who were unwavering in favor of conviction on the expressed ground that "they" cause all the trouble in the community. The First Circuit agreed that Rule 606(b) did not support inquiry on this basis, but held that this was one of the "rare and grave" cases where claims of racial or ethic bias implicated Villar's constitutional safeguards. The district court, as a result, had discretion to examine the validity of the verdict as against the biased statements of jurors.