From Glenn Huxtable

To those wondering about the reach of a Grand Jury, or even what a Grand Jury is ...

grand jury, in Anglo-American law, a group that examines accusations against persons charged with crime and, if the evidence warrants, makes formal charges on which the accused persons are later tried. Through the grand jury, laypersons participate in bringing suspects to trial. Though it holds judicial inquiries, the grand jury does not decide guilt or innocence. Its function is inquisitorial and accusatorial, unlike that of the petit jury, which tries cases. The grand jury’s function is to decide whether there is “probable cause” or “prima facie evidence” to believe that a person has committed a crime. Should it so decide, an indictment, a formal accusation of crime, is returned, and the accused must stand trial before a petit, or trial, jury whose duty is to determine the question of guilt “beyond a reasonable doubt.” The grand jury enjoys greater independence than the petit jury. It is instructed by the court prosecutor on questions of law and fact, but its investigations are relatively free from supervision. Although the jury works closely with the prosecutor, it is not formally under his control.