Cal. Civ. Proc. Code § 377.32
(a) The person who seeks to commence an action or proceeding or to continue a pending action or proceeding as the decedent’s successor in interest under this article, shall execute and file an affidavit or a declaration under penalty of perjury under the laws of this state stating all of the following:
(5) Either of the following, as appropriate, with facts in support thereof: