Warger v. Shauers, No. 13-517 (Sotomayor, J. for a unanimous Court) ---
Rule 606(b) of the Federal Rules of Evidence does not permit the introduction of an affidavit from one juror that alleges that another juror lied in response to voir dire questions for the purpose of concealing a potential source of bias.

The petitioner sued the respondent (so now I'll call the parties the plaintiff and defendant) in federal court over injuries resulting from a traffic accident. The jury found in favor of the defendant, but after trial one of the jurors told plaintiff's counsel that she had learned that the foreperson had lied in response to voir dire questions about potential biases. Armed with that affidavit, the plaintiff moved for a new trial. The district court denied the motion for a new trial, reasoning that the affidavit was inadmissible and without it there was no other evidence of concealed bias on the part of the foreperson. The Eighth Circuit and the Supreme Court both affirmed that decision.

This outcome, the Court said, was the simple result of the plain meaning of the words in Rule 606(b). That rule applies during an "inquiry into the validity of the verdict." Congress chose these words, the Court said, because it was rejecting a competing rule, adopted by some state courts, that permits juror testimony to expose bias on the part of other jurors. Because the affidavit here, if believed, would lead to setting aside the verdict as invalid, see McDonough Power Equip., Inc. v. Greenwood, 464 U.S. 548 (1984), the decision in Tanner v. United States, 483 U.S. 107 (1987), made the affidavit inadmissible. Finally, the canon of constitutional avoidance did not require admission of the affidavit. The canon only applies when there are plausible competing interpretations of the text, and here there weren't competing interpretations, one of which raised concerns about denying litigants their right to an impartial jury.

The decision is here:

http://www.supremecourt.gov/opinions/14pdf/13-517_7l48.pdf