Cal. Mil. & Vet. Code § 409.8

(a) In any proceeding under this chapter, a certificate signed by an appropriately authorized officer of the military department, branch, or unit in which a service member is serving shall be prima facie evidence as to any of the following facts stated in that certificate:
1. (1) That a person named has not been, is, or has been in the military service.
2. (2) The time when and the place where the person entered military service.
3. (3) The person’s residence at that time, and the rank, branch, and unit of the service that the person entered.
4. (4) The dates within which the person was in the military service.
5. (5) The monthly pay received by the person at the date of issuing the certificate.
6. (6) The time when and the place where the person died in or was discharged from the service.
(b) It shall be the duty of the authorized officer to furnish that certificate on application, and any certificate, when purporting to be signed by an officer purporting on the face of the certificate to have been so authorized, shall be prima facie evidence of its contents and of the authority of the signer to issue the certificate.
(c) Where a person in military service has been reported missing, they shall be presumed to continue in the service until accounted for, and no period herein limited that begins or ends with the death of the person shall begin or end until the death of the person is in fact reported to or found by the United States Department of Defense or any court or board thereof, or the Military Department or any court or board thereof, or until the person’s death is found by a court of competent jurisdiction.