When there is only one coroner-medical examiner on the staff, he or she shall be the chief coroner-medical examiner. When there is more than one coroner-medical examiner on the staff, the governing body shall designate one of them as the chief coroner-medical examiner. Until such designation, the person who has been longest in the continuous service of the county as coroner-medical examiner shall be the chief coroner-medical examiner.