As to each third-year law student or staff instructor authorized to assist a circuit public defender, there shall be kept on file in the office of the clerk of the court in the county where such authority is to be exercised the dean’s certificate, the student’s and instructor’s oaths, and the judge’s order as contemplated under Code Section 17-12-42. The authority to assist a circuit public defender as allowed under this Code section shall extend for no longer than 18 months. If during this period any change occurs in the status of the student or instructor at the law school in which he or she was enrolled or employed, that is, if the student ceases his or her enrollment, is suspended, or is expelled or if the instructor ceases his or her employment or is released by the school, any such authority shall terminate and be revoked.