When a civil suit reaches the stage of hearing and examination of witnesses:

The plaintiff has the right to begin

If the defendant admits the facts alleged by the plaintiff and contends that on some additional facts alleged by the defendant, the plaintiff is not entitled to any relief, the defendant has the right to begin

Both the plaintiff's ordinary right to begin and the defendant's right to begin where he admits the facts but relies on additional facts

Neither the plaintiff's ordinary right to begin nor the defendant's right to begin where he admits the facts but relies on additional facts