Cal. Evidence Code § 1041

(a) Except as provided in this section, a public entity has a privilege to refuse to disclose the identity of a person who has furnished information as provided in subdivision (b) purporting to disclose a violation of a law of the United States or of this state or of a public entity in this state, and to prevent another from disclosing the person’s identity, if the privilege is claimed by a person authorized by the public entity to do so and either of the following apply: (1) Disclosure is forbidden by an act of the Congress of the United States or a statute of this state. (2) Disclosure of the identity of the informer is against the public interest because the necessity for preserving the confidentiality of his or her identity outweighs the necessity for disclosure in the interest of justice. The privilege shall not be claimed under this paragraph if a person authorized to do so has consented that the identity of the informer be disclosed in the proceeding. In determining whether disclosure of the identity of the informer is against the public interest, the interest of the public entity as a party in the outcome of the proceeding shall not be considered. (b) The privilege described in this section applies only if the information is furnished in confidence by the informer to any of the following: (1) A law enforcement officer. (2) A representative of an administrative agency charged with the administration or enforcement of the law alleged to be violated. (3) Any person for the purpose of transmittal to a person listed in paragraph (1) or (2). As used in this paragraph, “person” includes a volunteer or employee of a crime stopper organization. (c) The privilege described in this section shall not be construed to prevent the informer from disclosing his or her identity. (d) As used in this section, “crime stopper organization” means a private, nonprofit organization that accepts and expends donations used to reward persons who report to the organization information concerning alleged criminal activity, and forwards the information to the appropriate law enforcement agency.