California Code of Civil Procedure > Code Civ. Proc. §116.520. Evidence; Witnesses
(a) The parties have the right to offer evidence by witnesses at the hearing or, with the permission of the court, at another time.
(b) If the defendant fails to appear, the court shall still require the plaintiff to present evidence to prove his or her claim.
(c) The court may consult witnesses informally and otherwise investigate the controversy with or without notice to the parties.