may, whether any particular person is charged or not, summon to the district court of his or her district any person whom he or she has reason to believe is capable of giving material evidence concerning such offence, and, if he or she thinks fit, bind the person by recognizance to appear for an initial hearing, if called upon by any Magistrate, at any time within the 6 months after the summons unless the person can show reasonable excuse to the contrary.