California Code, Government Code - GOV § 11445.60

(a) If the presiding officer has reason to believe that material facts are in dispute, the presiding officer may require a party to state the identity of the witnesses or other sources through which the party would propose to present proof if the proceeding were converted to a formal or other applicable hearing procedure.  If disclosure of a fact, allegation, or source is privileged or expressly prohibited by a regulation, statute, or the federal or state Constitution, the presiding officer may require the party to indicate that confidential facts, allegations, or sources are involved, but not to disclose the confidential facts, allegations, or sources.

(b) If a party has reason to believe that essential facts must be obtained in order to permit an adequate presentation of the case, the party may inform the presiding officer regarding the general nature of the facts and the sources from which the party would propose to obtain the facts if the proceeding were converted to a formal or other applicable hearing procedure.