In Arizona, a prosecutor can either file a direct complaint which leads to the preliminary hearing or they can send it to the Grand Jury and let them decide whether to charge the case or not. The Grand Jury is a secret hearing made up of 12 citizens. This is not a trial; it’s a formal procedure to determine if enough probable cause exists for an indictment. You will most likely not be present or even aware of this procedure and except in rare cases do not have a right to be there. It consists only of the 12 member Grand Jury, the Prosecutor, a witness of some kind, usually this a police officer or detective and a court reporter. Your defense attorney is not allowed to be present at this hearing nor is the judge.
The Grand Jury will hear the evidence in the case and be able to ask the witness questions, if they choose to do so. Then they will deliberate and decide to either charge the case or not. Remember this is not a trial, they are not determining guilt or innocence at this phase, only if there is enough probable cause to indict. As long as 9 of the 12 members of the grand jury say yes, we feel there is enough to indict, they will then decide what charges will be brought. They can add charges or subtract charges; they do not have to follow what the prosecutor presents. They then will return what is known as a “True Bill” which is the formal indictment document. You are now formally charged with a crime.
This, of course, is a general overview of the indictment process in Arizona. If it’s a Federal matter, those cases will always be decided by a Grand Jury.