Cal. Government Code § 11425.40

(a) The presiding officer is subject to disqualification for bias, prejudice, or interest in the proceeding. (b) It is not alone or in itself grounds for disqualification, without further evidence of bias, prejudice, or interest, that the presiding officer: (1) Is or is not a member of a racial, ethnic, religious, sexual, or similar group and the proceeding involves the rights of that group. (2) Has experience, technical competence, or specialized knowledge of, or has in any capacity expressed a view on, a legal, factual, or policy issue presented in the proceeding. (3) Has as a lawyer or public official participated in the drafting of laws or regulations or in the effort to pass or defeat laws or regulations, the meaning, effect, or application of which is in issue in the proceeding. (c) The provisions of this section governing disqualification of the presiding officer also govern disqualification of the agency head or other person or body to which the power to hear or decide in the proceeding is delegated. (d) An agency that conducts an adjudicative proceeding may provide by regulation for peremptory challenge of the presiding officer.