Jury: Legal Aspects

The Constitution's prohibition of double jeopardy precludes the review or revision of a jury's decision to acquit (United States v. Scott, 437 U.S. 82 (1978)), and review of a jury's decision to convict is highly deferential. In America, unlike most European nations, appellate review focuses more on trial and pretrial procedures than on trial outcomes.

In the federal courts and most states, juries are permitted to return inconsistent verdicts. When they do, courts assume that the jury verdict favorable to the defendant reflected a decision to be merciful; they disregard the possibility that the verdict unfavorable to the defendant was the product of error and misunderstanding (see Muller).

A common law rule forbids jurors from "impeaching" their verdicts by testifying to their own misconduct. In Tanner v. United States, 483 U.S. 107 (1987), the Supreme Court applied a successor to this rule and prevented two members of a jury from testifying that a number of jurors had abused alcohol, marihuana, and cocaine repeatedly during a trial. Although the rule was subject to an exception for testimony concerning "extraneous" or "outside" influences on the jury, the Court concluded that alcohol and drugs did not qualify. It declared, "There is little doubt that post-verdict 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."