California Code, Probate Code - PROB § 223

(a) As used in this section, “joint tenants” includes owners of property held under circumstances that entitled one or more to the whole of the property on the death of the other or others.

(b) If property is held by two joint tenants and both of them have died and it cannot be established by clear and convincing evidence that one survived the other, the property held in joint tenancy shall be administered or distributed, or otherwise dealt with, one-half as if one joint tenant had survived and one-half as if the other joint tenant had survived.

(c) If property is held by more than two joint tenants and all of them have died and it cannot be established by clear and convincing evidence that any of them survived the others, the property held in joint tenancy shall be divided into as many portions as there are joint tenants and the share of each joint tenant shall be administered or distributed, or otherwise dealt with, as if that joint tenant had survived the other joint tenants.