Code of Civil Procedure § 431.20
ARTICLE 2. Denials and Defenses
(a) Every material allegation of the complaint or cross-complaint, not controverted by the answer, shall, for the purposes of the action, be taken as true.
(b) The statement of any new matter in the answer, in avoidance or constituting a defense, shall, on the trial, be deemed controverted by the opposite party.