A jury is a sworn panel of persons (the jury) summoned to render an impartial judgment (a finding of fact on an issue) that is formally submitted to them by a court, or to pronounce a sentence or judgment. Juries developed in the Middle Ages in England and is a trademark of the Anglo-American common law system. They are still widely used today in Britain, the United States, Canada, Australia and other countries whose legal systems are derived from English legal traditions. The word jury is derived from the Anglo-Norman juror (“juror”). The jury is most often in the jurisdictions of the adversarial system of common law. In the modern system, jurors act as triers of fact, while judges act as Trier of law (see But annul). A trial without a jury (in which factual and legal issues are decided by a judge) is called a Bench Trial. In Scotland (with a separate legal system from England and Wales), the “not guilty” judgment was technically a form of jury annulment, but over time the interpretation has changed, so that the “not guilty” verdict has become normal when a jury is not found guilty and the “unproven” verdict is simply used, if the jury is not sure of innocence or guilt.  It is absolutely essential for Scottish and English rights that there is a presumption of innocence. This is not a trivial distinction, because any shift in the burden of proof constitutes a substantial change that undermines the protection of the citizen.  The size of juries varies according to their nature.
Grand juries are so called because they are generally larger than small juries of 12 to 23 members. Traditionally, small juries had 23 members, but the number is not fixed. In 1970, the U.S. Supreme Court held that the number 12 was not an essential element of jury trial (Williams v. Florida, 399 U.S. 78, 90 p. Ct. 1893, 26 L. Ed. 2d 446), and it sanctioned juries of no less than six members in criminal matters (Ballew v. Georgia, 435 U.p. 223, 98 pt.
1029, 55 L. Ed. 2d 234 ,1978). Parties in federal district courts and in many national courts may decide that the jury size is between six and 12. As a general rule, the jury of the Federal District Court is composed of six persons in civil matters. The institution of jury trial was ritually represented by Aischylos in The Eumenides, the third and final piece of his Oresteia trilogy.