39 C.F.R. § 3010.325 – Depositions.

(a) When permissible. The testimony of a witness may be taken by deposition when authorized by the Commission or the presiding officer on application of any party before the hearing is closed. An authorization to take the deposition of a witness will be issued only if:
1. (1) The person whose deposition is to be taken would be unavailable at the hearing;
2. (2) The deposition is deemed necessary to perpetuate the testimony of the witness; or
3. (3) The taking of the deposition is necessary to prevent undue and excessive expense to a party and will not result in undue delay or an undue burden to other parties.
(b) Application. An application for authorization to take testimony by deposition shall be filed with the Commission or the presiding officer and shall state:
1. (1) The name, identification, and post office address of the witness;
2. (2) The subject matter of the testimony.
3. (3) The time and place of taking the deposition;
4. (4) The name, identification, and post office address of the officer before whom the deposition is to be taken; and
5. (5) The reasons why the testimony of such witness should be taken by deposition.
(c) Authorization. If the application so warrants, the Commission or the presiding officer will issue and serve or cause to be served on the parties within a reasonable time in advance of the time fixed for taking testimony, an authorization for the taking of such testimony by deposition. Such authorization shall name the witness, the time, place, and officer before whom the deposition shall be taken, and shall specify the number of copies of the deposition to be submitted to the Commission. The authorization may include such terms and conditions as the Commission or the presiding officer deems fair and reasonable.
(d) Qualifications of officer before whom taken. Such deposition may be taken before a presiding officer or other authorized representative of the Commission, or any officer, not being counsel or attorney for any party or having an interest in the proceeding, authorized to administer oaths by the laws of the United States or of the place where the deposition is to be taken.
(e) Oath and reduction to writing. The officer before whom the deposition is to be taken shall put the witness on oath or affirmation and shall personally, or by someone acting under the officer's direction and in the officer's presence, record the examination of the witness. The examination shall be transcribed in the form specified in § 3010.124(a), signed by the witness, and certified in the usual form by the officer. The original of the deposition, together with the number of copies required by the authorization to be made by such officer, shall be forwarded by the officer to the Secretary by personal delivery or registered mail. Upon receipt, the Secretary shall hold the original for use in the hearing upon request by any party and shall make copies available for public inspection.
(f) Scope and conduct of examination. Unless otherwise directed in the authorization, the witness may be questioned regarding any matter which is relevant to the issues involved in the proceeding. Parties shall have the right for cross-examination and objection. In lieu of participation in the oral examination, parties may transmit written interrogatories to the officer who shall propound them to the witness.
(g) Objections. The officer before whom the deposition is taken shall not have the power to rule upon procedural matters or the competency, materiality, or relevancy of questions. Procedural objections or objections to questions of evidence shall be stated briefly and recorded in the deposition without argument. Objections not stated before the officer shall be deemed waived.
(h) When a part of the record. No portion of a deposition shall constitute a part of the record in the proceeding unless received in evidence by the presiding officer. If only a portion of the deposition is offered in evidence by a party, any other party may require the party to introduce all of it which is relevant to the part introduced, and any party may offer in evidence any other portions.
(i) Fees. Witnesses whose depositions are taken and the officer taking the same shall be entitled to the same fees as are paid for like services in the District Courts of the United States to be paid directly by the party or parties on whose application the deposition was taken.