45 CFR 501.4 - Witnesses.
(a) Examination of witnesses. Witnesses must appear in person and be examined orally under oath, except that for good cause shown, testimony may be taken by deposition.
(b) Witness fees and mileage. Witnesses summoned by the Commission on its own behalf or on behalf of a claimant or interested party will be paid the same fees and mileage that are allowed and paid witnesses in the District Courts of the United States. Witness fees and mileage will be paid by the Commission or by the party at whose request the witness appears.
(c) Transcript of testimony. Every person required to attend and testify will be entitled, upon payment of prescribed costs, to receive a copy of the recording of the testimony or a transcript of the recording. Every person required to submit documents or other evidence will be entitled to retain a copy thereof.