D.C. Code § 2-1403.10

In case of failure of conciliation efforts, or in advance of conciliation efforts, as determined by the Office, and after a finding of probable cause, the Office shall cause to be issued and served in the name of the Commission, a written notice, together with a copy of the complaint, as the same may have been amended, requiring the respondent to answer the charges of such complaint at a public hearing before 1 or more members of the Commission or before a hearing examiner, such hearing to be scheduled not less than 10 days or not more than 30 days after such service and at a place to be specified in such notice. Notice shall be served by registered or certified mail, return receipt requested, or by personal service.