A “hung jury,” also known as a “deadlocked jury,” is a jury whose members are unable to agree on a verdict by the required voting margin after extensive deliberations, resulting in a mistrial. It is up to the judge to determine whether the jury is “hung” or “deadlocked,” and the judge will make such a finding if he or she determines that further deliberations are unlikely to produce a verdict. When the judge declares the jury to be “hung” or “deadlocked,” a mistrial is declared, which brings the trial to an end without a determination on the merits. In the United States, a mistrial returns the parties to the positions they occupied before the trial began. so the government may re-try the defendant in a criminal case, and the plaintiff may proceed with another trial in a civil case.
Juries often report that they are hopelessly deadlocked, often after deliberating for only a short time. In some jurisdictions, judges will respond by reading an “Allen charge” at least once. An “Allen charge” is also known as a “dynamite charge” or “hammer charge” or sometimes simply “The Hammer.” It is a jury instruction based on the United States Supreme Court case Allen v. United States (1896), which approved of the practice. Although an Allen charge varies by jurisdiction and even from judge to judge, since its purpose is to prevent a hung jury, it generally calls jurors’ attention to the significant time and expense of a trial and urges them to reconsider their vote, especially if they are in the minority.
In most jurisdictions in the United States, juries must be unanimous to reach a verdict. In criminal cases, Oregon is the only state that allows non-unanimous jury verdicts, requiring only 10 of 12 jurors to reach a verdict. Such a practice may soon be declared unconstitutional, however, as the United States Supreme Court is currently considering the issue in the case of Ramos v. Louisiana. Louisiana recently amended its state constitution to require unanimous jury verdicts in criminal cases.
Non-unanimous jury verdicts are more common in civil cases, with perhaps as many as one-third of the states allowing for non-unanimous decisions of some kind. Nonetheless, a hung jury is still possible if the jury cannot reach the required supermajority for a verdict.