Except as otherwise provided in Code Section 24-6-616, at the request of a party the court shall order witnesses excluded so that each witness cannot hear the testimony of other witnesses, and it may make the order on its own motion. This Code section shall not authorize exclusion
of:
(1) A party who is a natural person;
(2) An officer or employee of a party which is not a natural person designated as its representative by its attorney; or
(3) A person whose presence is shown by a party to be essential to the presentation of the party’s cause.