Cal. Civ. Proc. Code § 2009

An affidavit may be used to verify a pleading or a paper in a special proceeding, to prove the service of a summons, notice, or other paper in an action or special proceeding, to obtain a provisional remedy, the examination of a witness, or a stay of proceedings, and in uncontested proceedings to establish a record of birth, or upon a motion, and in any other case expressly permitted by statute.