A jury is a sworn body of people (jurors) convened to hear evidence and render an impartial verdict (a finding of fact on a question) officially submitted to them by a court, or to set a penalty or judgment. Juries developed in England during the Middle Ages and are a hallmark of the English common law system. As such, they are used by the United Kingdom, the United States, Canada, Ireland, Australia, and other countries whose legal systems were derived from the British Empire. But most other countries use variations of the European civil law or Islamic sharia law systems, in which juries are not generally used. Most trial juries are "petit juries", and usually consist of twelve people. Historically, a larger jury known as a grand jury was used to investigate potential crimes and render indictments against suspects. All common law countries except the United States and Liberia have phased these out. The modern criminal court jury arrangement has evolved out of the medieval juries in England. Members were supposed to inform themselves of crimes and then of the details of the crimes. Their function was therefore closer to that of a grand jury than that of a jury in a trial. Etymology The word jury derives from Anglo-Norman juré ("sworn"). Juries are most common in common law adversarial-system jurisdictions. In the modern system, juries act as triers of fact, while judges act as triers of law (but see nullification). A trial without a jury (in which both questions of fact and questions of law are decided by a judge) is known as a bench trial. Types of jury Petit jury The "petit jury" (or "trial jury", sometimes "petty jury") hears the evidence in a trial as presented by both the plaintiff (petitioner) and the defendant (respondent) (also known as the complainant and defendant within the English criminal legal system). After hearing the evidence and often jury instructions from the judge, the group retires for deliberation, to consider a verdict. The majority required for a verdict varies. In some cases it must be unanimous, while in other jurisdictions it may be a majority or supermajority. A jury that is unable to come to a verdict is referred to as a hung jury. The size of the jury varies; in criminal cases involving serious felonies there are usually 12 jurors. In civil cases many trials require fewer than twelve jurors.