O.C.G.A. § 52-6-39 (2019)

When the attendance of any person shall be required as a witness before the commissioners in any matter or claim of which they shall have jurisdiction, it shall be the duty of their secretary, upon application, to issue subpoenas signed by him and directed to the persons whose attendance shall be required when such persons reside or shall be found in the county where such matters or claims may be pending. The summons shall express the cause and the party at whose action it is issued and shall be served as subpoenas of courts of record of this state are served at least 24 hours before the meeting of the commissioners to which it shall be returnable; but the subpoenas may be served by a messenger of the commissioners or by any sheriff or constable and the return of the messenger, sheriff, or constable shall be evidence of the service thereof.