Sometimes, it's tempting to serve someone when she is known to be coming to court for another matter. This is usually not permitted, but there are exceptions.

Generally,

a suitor or a witness in attendance upon the trial of any case in court, is privileged from arrest under any civil process, and is exempted from the service of any writ or summons upon him or them while in attendance upon such court, or in going to or returning therefrom.

Steelman v. Fowler, 234 Ga. 706, 217 S.E.2d 285 (1975).

There are two exceptions. First, “it does not apply to criminal defendants or nonresidents, who are in this state temporarily ‘for some purpose other than to appear in court as a party or witness.’” Loiten v. Loiten, 288 Ga. App. 638, 655 S.E.2d 265 (2007)citing Ausbon v. Ausbon, 131 Ga. App. 530, 531, 206 S.E.2d 546 (1974).

Second, it only protects “a party in attendance upon the trial of a case from service of process in a new action.” Blalock v. Blalock, 247 Ga. 548, 550, 277 S.E.2d 655 (1981). For instance, a party suing for contempt could be served in court with a modification of custody matter which was actually a part of the same matter. Id.

In Loiten, the defendant appeared at trial to contest a restraining order entered against him ex parte for which he was not properly served (he received the order but not the petition). At the hearing, the trial court asked him to waive service which he refused. The court then instructed the sheriff to serve the defendant in the parking lot. On appeal, the service was found to be ineffective. Id. at 638. The court held that although an ex parte hearing had been previously had, the matter was new to the defendant and therefore he was protected by the Steelman rule.