D.C. Code § 22-3011
Defenses to child sexual abuse and sexual abuse of a minor.
(a) Neither mistake of age nor consent is a defense to a prosecution under §§ 22-3008 to 22-3010.01 , prosecuted alone or in conjunction with charges under § 22-3018 or § 22-403 .
(b) Marriage or domestic partnership between the defendant and the child or minor at the time of the offense is a defense, which the defendant must establish by a preponderance of the evidence, to a prosecution under §§ 22-3008 to 22-3010.01 , prosecuted alone or in conjunction with charges under § 22-3018 or § 22-403 , involving only the defendant and the child or minor.