A grand jury is presented with evidence from the U.S. attorney, the prosecutor in federal criminal cases. The grand jury determines whether there is “probable cause” to believe the individual has committed a crime and should be put on trial. If the grand jury determines there is enough evidence, an indictment will be issued against the defendant.
Grand juries are comprised of twenty-three members, plus alternates. A quorum of sixteen members is required to conduct business. Twelve members must vote for a “true bill” before an indictment can be issued. All grand jury proceedings are conducted in secret.
Handbook for Federal Grand Jurors