The appellant, his/her representative, counsel or other representative of the department, an interpreter if the appellant does not speak English or is deaf and an interpreter has been requested, witnesses for both parties, persons who may be called as witnesses by the hearing officer and such other persons or members of the public as the hearing officer in his/her discretion may admit, are entitled to be present at the hearing. Supervisory staff of the department shall be entitled to observe or to assist the official representative of the department, as necessary for proper supervision and evaluation of the performance of the employee.