Cal. Government Code § 11511

On verified petition of any party, an administrative law judge or, if an administrative law judge has not been appointed, an agency may order that the testimony of any material witness residing within or without the state be taken by deposition in the manner prescribed by law for depositions in civil actions under Title 4 (commencing with Section 2016.010) of Part 4 of the Code of Civil Procedure. The petition shall set forth the nature of the pending proceeding; the name and address of the witness whose testimony is desired; a showing of the materiality of the testimony; a showing that the witness will be unable or cannot be compelled to attend; and shall request an order requiring the witness to appear and testify before an officer named in the petition for that purpose. The petitioner shall serve notice of hearing and a copy of the petition on the other parties at least 10 days before the hearing. Where the witness resides outside the state and where the administrative law judge or agency has ordered the taking of the testimony by deposition, the agency shall obtain an order of court to that effect by filing a petition therefor in the superior court in Sacramento County. The proceedings thereon shall be in accordance with the provisions of Section 11189.