D.C. Mun. Regs. tit. 23, § 1615
1615.1 At the request of a party, or on its own motion, and subject to § 1615.2, the Board shall order witnesses excluded so that they will not hear the testimony of other witnesses.
1615.2 Notwithstanding § 1615.1, the following persons shall not be excluded from hearings before the Board:
(a) The Applicant or the Licensee;
(b) The Designated Representative for a party to a proceeding; or
(c) Any person whose presence is shown by a party to be essential to the presentation of his or her case.
SOURCE: Final Rulemaking published at 63 DCR 3727 (March 11, 2016); as amended by Final Rulemaking published at 66 DCR 1822 (February 8, 2019).