If a defendant is indigent and unable to pay for witnesses desired by him in addition to those summoned at the expense of the parish, he shall make a sworn application to the court for the additional witnesses. The application must allege that the testimony is relevant and material and not cumulative and that the defendant cannot safely go to trial without it.

The court shall make a private inquiry into the facts, and if satisfied that the defendant is entitled to the privilege, it shall render an order permitting the defendant to subpoena additional witnesses at the expense of the parish. If the application is denied, the court shall state the reasons for the denial in writing, which shall become part of the record.