D.C. Code § 48-905.06
In a proceeding for a violation of this chapter, the official report of chain of custody and of analysis of a controlled substance performed by a chemist charged with an official duty to perform such analysis, when attested to by that chemist and by the officer having legal custody of the report and accompanied by a certificate under seal that the officer has legal custody, shall be admissible in evidence as evidence of the facts stated therein and the results of that analysis. A copy of the certificate must be furnished upon demand by the defendant or his or her attorney in accordance with the rules of the Superior Court of the District of Columbia or, if no demand is made, no later than 5 days prior to trial. In the event that the defendant or his or her attorney subpoenas the chemist for examination, the subpoena shall be without fee or cost and the examination shall be as on cross-examination.
D.C. Code § 48-905.06