A grand jury is a specially appointed body that determines whether a prosecutor has gathered enough evidence to warrant a trial in a particular case. Used only in special cases, the grand jury serves as a conduit through which reasonable cases pass into the traditional trial system. The role of the grand jury is to determine whether the evidence gathered by a district, state, or federal prosecuting attorney creates a justifiable basis for an indictment. Though once used throughout the United Kingdom and some of Europe, modern-day grand juries exist primarily in the United States.
The origin of this type of jury dates back to medieval times, although the role of the grand jury in those days was quite distinct. Beginning in the 12th century in England, a grand jury served as the primary accusers in a trial. Since judges were itinerant and not always familiar with the area, they relied on a local jury to present cases when they visited a region. 14th century laws updated this procedure by splitting the role of the grand jury between two separate bodies: a grand jury that served as the accusers, and a petit jury that determined guilt or innocence. It was under this system that the modern role of the grand jury developed, as the accusatory jury began to serve as a pre-trial body that examined evidence brought by the crown's representatives, rather than making accusations of their own accord.
Though now abandoned throughout most of Europe and the modern-day United Kingdom, the grand jury plays an important part in the judicial system of the United States. Grand juries may be impaneled by federal, state, and even regional courts in some cases. Most often, grand juries are impaneled before felony charges can be brought, in recognition of the fact that felony charges are extremely serious in nature and require due diligence to ensure that they are not used lightly or unfairly.
The role of a grand jury can be split into distinct categories: evidence examination and investigation. Many juries act in an examining role, reviewing the evidence presented by the prosecutor in order to determine if, and which, charges should be filed. Some grand juries, often referred to as “special” grand juries, can also investigate a situation on their own, including summoning witnesses and subpoenaing confidential documents. Special grand juries are often used to investigate possible organized criminal activity, but may also be used to examine the possibility of political or government corruption.