Cal. Gov. Code § 21169

The writ of review shall be made returnable not later than 30 days after the date of issuance thereof, and shall direct the Workers’ Compensation Appeals Board to certify its record in the case to the court. On the return day the cause shall be heard in the court unless continued for good cause. No new or additional evidence shall be introduced in the court, but the cause shall be heard on the record of the appeals board, as certified to by it.