The district attorney shall institute proceedings before magistrates for the arrest of persons charged with or reasonably suspected of public offenses when he has information that such offenses have been committed. For that purpose, when not engaged in criminal proceedings in the superior court or in civil cases on behalf of the people, he shall attend upon the magistrates in cases of arrest when required by them and shall attend before and give advice to the grand jury whenever cases are presented to it for its consideration.
Ca. Gov. Code § 26501