At a party’s request, the court must order witnesses excluded so that they cannot hear other witnesses’ testimony. Or the court may do so on its own. But this rule does not authorize excluding:
(a) a party who is a natural person and, in civil cases, that person’s spouse;
(b) after being designated as the party’s representative by its attorney:
(1) in a civil case, an officer or employee of a party that is not a natural person; or
(2) in a criminal case, a defendant that is not a natural person;
(c) a person whose presence a party shows to be essential to presenting the party’s claim or defense; or
(d) the victim in a criminal case, unless the court determines that the victim’s testimony would be materially affected by hearing other testimony at the trial.