D.C. Mun. Regs. tit. 4 § 117
The Hearing Examiner shall conduct the hearing so as to bring out pertinent facts, including the production of pertinent documents.
The Hearing Examiner shall permit wide latitude in the introduction of evidence, but shall exclude irrelevant and unduly repetitious evidence.
The Hearing Examiner shall receive only evidence which may have a bearing upon the complaint or upon any other employment policy or practice related to the complaint.
District government employees shall be required to serve as witnesses at hearings held under the provisions of this chapter. Absence from regular duty to serve as a witness shall be without charge to leave or loss in pay.
Witnesses may be requested by either party, subject to the approval of the Hearing Examiner of the reasons given by either party as to the need for the witnesses.
The Hearing Examiner shall request the Director to make available at the hearing as a witness, through subpoena, any District government employee whose appearance is deemed necessary.
The Hearing Examiner shall request the Director to make available at the hearing any other person, through subpoena, whose appearance the Hearing Examiner deems necessary.
The denial of a request for the appearance of a person as a witness by the Hearing Examiner shall include the reasons for denial and shall be entered into the record of the hearing.
Requests for witnesses may be submitted to the Director in writing by either party not later than three (3) working days in advance of the scheduled hearing date.
Each agency head shall make employees available to serve as witnesses whenever it is administratively possible and practicable to do so.
Reasons for denial by an agency head of a request for the service of an employee as a witness shall be sent in writing to the Director, along with a copy to the Hearing Examiner for inclusion in the complaint record and the hearing record.
If the agency head's explanation is deemed inadequate, the Hearing Examiner shall so advise the Director and request the Director to order, through subpoena, the employee to be made available as a witness at the hearing.
An agency head shall be required to make the employee available when directed by notice from the Director.
If the agency head's explanation is adequate, the Hearing Examiner shall insert it in the record of the hearing, provide a copy to the requesting party and the agency, and make arrangements to secure testimony from the employee through written interrogatories.
Witnesses shall not be subjected to restraint, interference, coercion, discrimination, intimidation, or reprisal in connection with their testimony.
D.C. Mun. Regs. Tit. 4, § 117