A Hearing Officer shall not participate in the conduct of a hearing if he is prejudiced with respect to any party, or has a conflict of interest, financial or otherwise, in the matter pending. Personal or professional acquaintance is not a valid basis for disqualification. Any party may suggest to the Secretary the possibility of the existence of grounds for disqualification, provided it is made in writing and prior to the date set for the hearing. The decision of the Secretary as to the qualification or disqualification of the Hearing Officer shall be final.
651 CMR, § 9.10