||The examples and perspective in this article may not represent a worldwide view of the subject. (November 2010)|
A hung jury or deadlocked jury is a jury that cannot, by the required voting threshold, agree upon a verdict after extended deliberation and is unable to change its votes. Hung jury may also be referred to as a non unanimous verdict. 
In Canada, the jury must reach a unanimous decision on criminal cases but not in civil cases. If the jury cannot reach a unanimous decision, a hung jury is declared. A new panel of jurors will be selected for the new trial.
England and Wales
In England and Wales a majority of 10–2 (10–1 if only eleven jurors remain) is needed for a verdict; failure to reach this may lead to a retrial.
Initially, the jury will be directed to try to reach a unanimous verdict. If they fail to reach a unanimous verdict, the judge may later (after not less than two hours) give directions that a majority verdict will be acceptable, but still no less than ten to two, although the jury should continue to try to reach a unanimous verdict if possible.
When the jury are called to deliver a verdict after majority directions have been given, a careful protocol of questions is followed: only in the event of a guilty verdict is it then asked whether or not all jurors were agreed on that verdict. This is to ensure that any not-guilty verdict is not tainted by it being disclosed that any jurors dissented. This protocol is followed separately for each charge.
It is not possible to have a hung jury in Scotland in criminal cases. Juries consist of 15, and verdicts are decided by simple majority. If jurors drop out because of illness or another reason, the trial can continue with a minimum of 12 jurors, but the support of 8 jurors is still needed for a guilty verdict; anything less is treated as an acquittal.
In civil cases there is a jury of 12, with a minimum of 10 needed to continue the trial. It is possible to have a hung jury if there is a tied vote after three hours' deliberation.
In the United States, the result is a mistrial, and the case may be retried. Some jurisdictions permit the court to give the jury a so-called Allen charge, inviting the dissenting jurors to re-examine their opinions, as a last-ditch effort to prevent the jury from hanging. The Federal Rules of Criminal Procedure state, "The verdict must be unanimous...If there are multiple defendants, the jury may return a verdict at any time during its deliberations as to any defendant about whom it has agreed...If the jury cannot agree on all counts as to any defendant, the jury may return a verdict on those counts on which it has agreed...If the jury cannot agree on a verdict on one or more counts, the court may declare a mistrial on those counts. A hung jury does not imply either the defendant's guilt or innocence. The government may retry any defendant on any count on which the jury could not agree."
Juries in criminal cases are generally, as a rule, required to reach a unanimous verdict, while juries in civil cases typically have to reach a majority on some level. If a defendant has been found guilty of a capital offense (one that could result in the death penalty if the person is eligible) then the opinion of the jury must be unanimous if the defendant is to be sentenced to death. Currently, two states, Oregon and Louisiana, do not require unanimous verdicts in criminal cases. Each requires a 10–2 majority for conviction, except for capital crimes: Oregon requires at least 11 votes and Louisiana requires all 12.
In jurisdictions giving those involved in the case a choice of jury size (such as between a six-person and twelve-person jury), defense counsel in both civil and criminal cases frequently opt for the larger number of jurors. A common axiom in criminal cases is that "it takes only one to hang," referring to the fact that, in some cases, a single juror can defeat the required unanimity.
One proposal for dealing with the difficulties associated with hung juries has been to introduce supermajority verdicts. This measure would allow juries to convict defendants without unanimous agreements amongst the jurors. Hence, a 12-member jury that would otherwise be deadlocked at 11 for conviction and 1 against, would be recorded as a guilty verdict. The rationale for majority verdicts usually includes arguments involving so-called 'rogue jurors' who unreasonably impede the course of justice. Opponents of majority verdicts argue that it undermines public confidence in criminal justice systems and results in a higher number of individuals convicted of crimes they did not commit.
In United States military justice, the Uniform Code of Military Justice (10 U.S.C. Chapter 47) Article 52 specifies the minimum number of court martial panel members required to return a verdict of guilty. In cases that involve a mandatory death sentence, a unanimous vote of all panel members is required. In cases that involve mandatory life sentences or sentences of confinement over ten years, a three-fourths vote is required. In all other cases, only a two-thirds vote is required to convict. Additionally, the Manual for Courts-Martial requires only a judge and a specified number of panel members (five for a general court-martial or three for a special court-martial; no panel is seated for a summary court-martial) in all non-capital cases. In capital cases, a panel of 12 members is required.
- West's Business Law, Alternate Edition (Hardcover)
- "Canada's System of Justice: The Role of the Public". Department of Justice. 2011-12-05.
- Juries Act 1974, subsection 17(4)
- Ministry of Justice Criminal Procedure Rules: Crown court practices: Majority verdicts[dead link]
- Criminal Procedure (Scotland) Act 1995 section 90
- Rule 31, Federal Rules of Criminal Procedure