California Code, Labor Code - LAB § 5271

(a) The parties to a dispute submitted for arbitration may select any eligible attorney from the list prepared by the presiding workers' compensation judge to serve as arbitrator.However, when the disputed issue involves insurance coverage, the parties may select any attorney as arbitrator upon agreement of the parties.

(b) If the parties cannot select an arbitrator by agreement, either party may request the presiding workers' compensation judge to assign a panel of five arbitrators selected at random from the list of eligible attorneys.No more than three arbitrators on a five-member panel may be defense attorneys, no more than three may be applicant's attorneys, and no more than two may be retired workers' compensation judges or appeals board commissioners.

(c) For each party in excess of one party in the capacity of employer and one party in the capacity of injured employee or lien claimant, the presiding judge shall randomly select two additional arbitrators to add to the panel. For each additional party in the capacity of employer, the presiding judge shall assign a retired workers' compensation judge or retired appeals board commissioner and an applicant's attorney. For each additional party in the capacity of injured employee or lien claimant, the presiding judge shall assign a retired workers' compensation judge or retired appeals board commissioner and a defense attorney. For each additional other party, the presiding judge shall assign two arbitrators to the panel, in order of rotation from case to case, as follows: a retired workers' compensation judge or retired appeals board commissioner, an applicant's attorney, a defense attorney.

(d) A party may petition the presiding workers' compensation judge to remove a member from the panel pursuant to Section 170.1 of the Code of Civil Procedure. The presiding workers' compensation judge shall assign another eligible attorney to replace any member removed under this subdivision.

(e) Each party or lien claimant shall strike two members from the panel, and the remaining attorney shall serve as arbitrator.