CA Gov't Code Section 11425.30

(a)

A person may not serve as presiding officer in an adjudicative proceeding in any of the following circumstances:

(1)

The person has served as investigator, prosecutor, or advocate in the proceeding or its preadjudicative stage.

(2)

The person is subject to the authority, direction, or discretion of a person who has served as investigator, prosecutor, or advocate in the proceeding or its preadjudicative stage.

(b)

Notwithstanding subdivision (a):

(1)

A person may serve as presiding officer at successive stages of an adjudicative proceeding.

(2)

A person who has participated only as a decisionmaker or as an advisor to a decisionmaker in a determination of probable cause or other equivalent preliminary determination in an adjudicative proceeding or its preadjudicative stage may serve as presiding officer in the proceeding.

(c)

The provisions of this section governing separation of functions as to the presiding officer also govern separation of functions as to the agency head or other person or body to which the power to hear or decide in the proceeding is delegated.