Cal. Lab. Code § 6623

Any decision of the appeals board granting or denying a petition for reconsideration or affirming, rescinding, altering, or amending the original findings, order, or decision following reconsideration shall be made by the appeals board and not by a hearing officer and shall be in writing, signed by a majority of the appeals board members assigned thereto, and shall state the evidence relied upon and specify in detail the reasons for the decision.