No person shall be held to answer for any felony or criminal offense of any grade, unless on presentment or indictment of a grand jury or on information of the public prosecutor, after a commitment by a magistrate, except in cases of impeachment, in cases cognizable by probate courts or by justices of the peace, and in cases arising in the militia when in actual service in time of war or public danger; provided, that a grand jury may be summoned upon the order of the district court in the manner provided by law, and provided further, that after a charge has been ignored by a grand jury, no person shall be held to answer, or for trial therefor, upon information of public prosecutor.