D.C. Code § 14-101: Evidence under oath; affirmation in lieu of oath; perjury.

(a)

All evidence shall be given under oath according to the forms of the common law.

(b)

A witness who has conscientious scruples against taking an oath, may, in lieu thereof, solemnly, sincerely, and truly declare and affirm. Where an application, statement, or declaration is required to be supported or verified by an oath, the affirmation is the equivalent of an oath.

(c)

Whoever swears, affirms, declares, or gives testimony in any form, where an oath is authorized by law, is lawfully sworn, and is guilty of perjury in a case where he would be guilty of that crime if sworn according to the forms of the common law.