Grand juries in the United States

Grand juries in the United States are groups of citizens empowered by United States federal or state law to conduct legal proceedings, chiefly investigating potential criminal conduct and determining whether criminal charges should be brought. The grand jury originated under the law of England and spread through colonization to other jurisdictions as part of the common law. Today, however, the United States is one of only two jurisdictions, along with Liberia, that continues to use the grand jury to screen criminal indictments.[1][2]

Generally speaking, a grand jury may issue an indictment for a crime, also known as a "true bill," only if it verifies that those presenting had probable cause to believe that a crime has been committed by a criminal suspect.[3] Unlike a petit jury, which resolves a particular civil or criminal case, a grand jury (typically having twelve to twenty-three members) serves as a group for a sustained period of time in all or many of the cases that come up in the jurisdiction, generally under the supervision of a federal U.S. attorney, a county district attorney, or a state attorney-general, and hears evidence ex parte (i.e. without suspect or person of interest involvement in the proceedings).

The federal government is required to use grand juries for all felonies, though not misdemeanors, by the Fifth Amendment to the United States Constitution. While all states in the U.S. currently have provisions for grand juries,[4] only half of the states actually employ them[5] and twenty-two require their use, to varying extents.[6] The modern trend is to use an adversarial preliminary hearing before a trial court judge, rather than grand jury, in the screening role of determining whether there is evidence establishing probable cause that a defendant committed a serious felony before that defendant is required to go to trial and risk a conviction on those charges.

Some states have "civil grand juries," "investigating grand juries," or the equivalent, to oversee and investigate the conduct of government institutions, in addition to dealing with criminal indictments.[7][8][9][10][11]