Purpose of a Grand Jury
A grand jury is used in the U.S. to protect people from unjustifiable and unfair prosecution. The grand jury, composed of 12 to 23 everyday citizens, reviews evidence, and hears testimony for the purpose of conducting an investigation into alleged criminal conduct. Such grand jury investigations take place behind closed doors, testimony being kept secret, in order to encourage witnesses to testify freely. If there is sufficient evidence presented to warrant the defendant being charged with the crime, and put on trial, the grand jury issues an indictment.
When a true bill indictment is issued, it results in the defendant being criminally charged, and the move toward trial begins. When a no true bill is issued, most people never even know the matter was heard by a grand jury, as these proceedings take place confidentially.