Cal. Probate Code § 21611

The spouse shall not receive a share of the estate under Section 21610 if any of the following is established: (a) The decedent’s failure to provide for the spouse in the decedent’s testamentary instruments was intentional and that intention appears from the testamentary instruments. (b) The decedent provided for the spouse by transfer outside of the estate passing by the decedent’s testamentary instruments and the intention that the transfer be in lieu of a provision in said instruments is shown by statements of the decedent or from the amount of the transfer or by other evidence. (c) The spouse made a valid agreement waiving the right to share in the decedent’s estate. (d) (1) If both of the following apply: (A) The spouse was a care custodian, as that term is defined in Section 21362, of the decedent who was a dependent adult, as that term is defined in Section 21366, and the marriage commenced while the care custodian provided services to the decedent, or within 90 days after those services were last provided to the decedent. (B) The decedent died less than six months after the marriage commenced. (2) Notwithstanding paragraph (1), a spouse described by this subdivision shall be entitled to receive a share of the estate pursuant to Section 21610 if the spouse proves by clear and convincing evidence that the marriage between the spouse and the decedent was not the product of fraud or undue influence.