D.C. Code § 16-1907: Traversing return; pleading; witnesses.

A person at whose instance or in whose behalf a writ of habeas corpus has been issued may traverse the return thereto, or plead any matters showing that there is not a sufficient legal cause for his confinement or detention. The court or judge may issue process for witnesses or for the production of papers, which shall be served and enforced in like manner as similar process issued in a cause pending in the court, if the court or judge is satisfied as to the materiality of the testimony proposed to be adduced.