When someone accused of a crime goes to court, a decision is made on whether or not to punish them. This is done by either a judge or a jury. A judge has a job in law. But a jury is a group of everyday people who work together to decide if a suspect is innocent or guilty. Whether or not a jury is used depends on the matter being heard. In general, courts draw on juries when the matter is particularly serious. But to understand when and why a jury is used, it helps to know more about justice systems.