generally the request to convene a grand jury is when a prosecutor feels there is sufficient evidence to subpoena parties, issue search warrants and sworn testimony and ultimately issue indictments.
Its not something you do unless you very seriously believe that a crime may have happened, and need to formally pull together the evidence to press criminal charges.
Its not something you do unless you very seriously believe that a crime may have happened, and need to formally pull together the evidence to press criminal charges.