1. The grand jury is not bound to hear evidence for the defendant, except that the defendant is entitled to submit a statement which the grand jury must receive providing whether a preliminary hearing was held concerning the matter and, if so, that the evidence presented at the preliminary hearing was considered insufficient to warrant holding the defendant for trial. It is their duty, however, to weigh all evidence submitted to them, and when they have reason to believe that other evidence within their reach will explain away the charge, they shall order that evidence to be produced, and for that purpose may require the district attorney to issue process for the witnesses.
2. If the district attorney is aware of any evidence which will explain away the charge, the district attorney shall submit it to the grand jury.
3. The grand jury may invite any person, without process, to appear before the grand jury to testify.