Cal. Welf. and Inst. Code § 4022
When complaint is made to the department regarding the officers or management of a hospital or institution for persons with mental health disorders, or regarding the management of a person detained therein or regarding a person held in custody as having a mental health disorder, the department may, before making an examination regarding the complaint, require it to be made in writing and sworn to before an officer authorized to administer oaths. On receipt of such a complaint, sworn to if so required, the department shall direct that a copy of the complaint be served on the authorities of the hospital or institution or the person against whom complaint is made, together with notice of the time and place of the investigation, as the department directs.
Ca. Welf. and Inst. Code § 4022