CCP §641: A party may object to the appointment of any person as referee, on one or more of the following grounds: (a) A want of any of the qualifications prescribed by statute to render a person competent as a

A party may object to the appointment of any person as referee, on one or more of the following grounds: (a) A want of any of the qualifications prescribed by statute to render a person competent as a juror, except a requirement of residence within a particular county in the state. (b) Consanguinity or affinity, within the third degree, to either party, or to an officer of a corporation which is a party, or to any judge of the court in which the appointment shall be made. (c) Standing in the relation of guardian and ward, conservator and conservatee, master and servant, employer and clerk, or principal and agent, to either party; or being a member of the family of either party; or a partner in business with either party; or security on any bond or obligation for either party. (d) Having served as a juror or been a witness on any trial between the same parties. (e) Interest on the part of the person in the event of the action, or in the main question involved in the action. (f) Having formed or expressed an unqualified opinion or belief as to the merits of the action. (g) The existence of a state of mind in the potential referee evincing enmity against or bias toward either party.