33 U.S.C. § 924: Witnesses

No person shall be required to attend as a witness in any proceeding before a deputy commissioner at a place outside of the State of his residence and more than one hundred miles from his place of residence, unless his lawful mileage and fee for one day’s attendance shall be first paid or tendered to him; but the testimony of any witness may be taken by deposition or interrogatories according to the rules of practice of the Federal district court for the judicial district in which the case is pending (or of the United States District Court for the District of Columbia if the case is pending in the District).