D.C. Code § 28:3-119: Notice of right to defend action.

In an action for breach of an obligation for which a third person is answerable over pursuant to this article or Article 4, the defendant may give the third person notice of the litigation in a record, and the person notified may then give similar notice to any other person who is answerable over. If the notice states (i) that the person notified may come in and defend and (ii) that failure to do so will bind the person notified in an action later brought by the person giving the notice as to any determination of fact common to the 2 litigations, the person notified is so bound unless after seasonable receipt of the notice the person notified does come in and defend.