The Fifth Amendment requirement that serious federal criminal charges be started by a grand jury (a group of citizens who hear evidence from a prosecutor about potential crimes) is rooted in English common law. Its basic purpose is to provide a fair method for beginning criminal proceedings against those accused of committing crimes.
Grand jury charges can be issued against anyone except members of the military, who are instead subject to courts-martial in the military justice system. A significant number of states do not use grand juries; instead they begin criminal proceedings using informations or indictments. The right to a grand jury is one of only a few protections in the Bill of Rights that has not been applied to the states by the 14th Amendment.
The United States Constitution, What It Says, What It Means, A Hip Pocket Guide