D.C. Code § 23-106: Witnesses for defense; fees.

The court shall order at any time that a subpoena be issued for service upon a named witness on behalf of a defendant if the defendant makes an application for such an order and makes a satisfactory showing that he is financially unable to pay the fees of the witness and that the presence of the witness is necessary to an adequate defense. If the court orders the subpoena to be issued the costs incurred by the process and the fees of the witness so subpoenaed shall be paid in the same manner in which similar costs and fees are paid in case of a witness subpoenaed in behalf of the prosecuting authority.