Answer:
Some states still use the Grand Jury system of indicting criminal defendants. The police arrest a subject - deliver the investigation to the Prosecutor's office - who presents the case to a Grand Jury - who decides if there was probable cause for the arrest and that there is enough evidence to send the subject to trial. If they do, an indictment of that subject is prepared and 'handed down' formally charging the defendant of his crime. If they decide there is insufficient evidence of a crime they return a 'no bill' of indictment.