At the request of a party the court shall order witnesses excluded so that they cannot hear the testimony of other witnesses, and it may make the order of its own motion. This rule does not authorize exclusion of:
(1) a party who is a natural person or in civil cases the spouse of such natural person;
(2) an officer or employee of a party in a civil case or a defendant in a criminal case that is not a natural person designated as its representative by its attorney;
(3) a person whose presence is shown by a party to be essential to the presentation of the party’s cause; or
(4) the victim in a criminal case, unless the victim is to testify and the court determines that the victim’s testimony would be materially affected if the victim hears other testimony at the trial.