A subpoena may be served by any sheriff, by his or her deputy, or by any other person not less than 18 years of age. Proof may be shown by return or certificate endorsed on a copy of the subpoena. Subpoenas may also be served by registered or certified mail or statutory overnight delivery, and the return receipt shall constitute prima-facie proof of service. Service upon a party may be made by serving his or her counsel of record.
OCGA § 24-13-24