Each district attorney may, when he cannot prosecute a case for ethical reasons or other good cause, appoint a practicing member of the bar of this state to act as special assistant district attorney. Any person so appointed shall have authority to act only in the specific case or matter for which the appointment was made. An appointment and oath shall be required of special assistant district attorneys in substantially the same form as that required for assistant district attorneys in Section 36-1-2 N.M. Stat. Ann..