<P> 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 . </P> <P> The word 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 . </P> <P> 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). 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 . </P> <P> In civil cases many trials require fewer than twelve jurors . </P>

How many jury members in a criminal trial