(a) Witnesses at the hearing shall testify under oath or affirmation. The administrative law judge and the parties may question witnesses with respect to any matters relevant and material to any contested issue. Any party who intends to present the testimony of an expert witness at a hearing shall so notify all other parties to the claim at least 10 days before the hearing. The failure to give notice of the appearance of an expert witness in accordance with this paragraph, unless notice is waived by all parties, shall preclude the presentation of testimony by such expert witness.
(b) No person shall be required to appear as a witness in any proceeding before an administrative law judge at a place more than 100 miles from his or her place of residence, unless the lawful mileage and witness fee for 1 day's attendance is paid in advance of the hearing date.