Unless otherwise provided by law, there shall be no verbal communications with the hearings examiner regarding any issue of fact or law in a contested case without notice and opportunity for all parties to participate, and there may be no written communications that are not transmitted at the same time to all parties, except that an individual involved in rendering the decision in a contested case may communicate ex parte with employees of the agency who did not participate in the hearing for the purpose of utilizing their special skills or knowledge in evaluating the evidence.