D.C. Mun. Regs. tit. 1, r. 1-2003
Within ten (10) days of any policeman's or fireman's making a claim against, or instituting a proceeding against, or entering in a settlement negotiations with, a third person as a result of any injury or disease for which the policeman or fireman has received care from the District, the policeman or fireman shall provide written notice of the same by mailing the notice first class to the Corporation Counsel and to the Chief of Police or Fire Chief, respectively.
The policeman or fireman shall also provide written notice of the District's lien interest to the third party at the time of making a claim or instituting a proceeding or entering into settlement negotiations.
Whenever the Corporation Counsel separately institutes a proceeding against such a third party, the Corporation Counsel shall send written notice to the policeman or fireman treated, setting forth the District's right to reimbursement and the policeman's or fireman's right, if he or she has not proceeded to trial in another proceeding or executed a settlement agreement, to intervene or join in the District's proceeding and to retain private counsel.
D.C. Mun. Regs. tit. 1, r. 1-2003