Cal. Gov. Code § 83115.5
A finding of probable cause to believe this title has been violated shall not be made by the commission unless, at least 21 days prior to the commission's consideration of the alleged violation, the person alleged to have violated this title is notified of the violation by service of process or registered mail with return receipt requested, provided with a summary of the evidence, and informed of that person's right to be present in person and represented by counsel at any proceeding of the commission held for the purpose of considering whether probable cause exists for believing the person violated this title. Notice to the alleged violator shall be deemed made on the date of service, the date the registered mail receipt is signed, or, if the registered mail receipt is not signed, the date returned by the post office. A proceeding held for the purpose of considering probable cause shall be private unless the alleged violator files with the commission a written request that the proceeding be public.
Ca. Gov. Code § 83115.5