«A Comparative study on the principle of immutability of litigation in Iranian and American law»

Based on «the principle of immutability of litigation», although parties to the dispute have dominance on the thematic elements of legal claim, but also when the petition was set by the plaintiff, all of wanted things must be stipulated clearly in the offered petition by lawful condition observance, and also the defendant has defense right, under this required framework. After the trial begins, next changes have limitations which are followed in whole trial. The purpose of this principle is showing that although parties have free hearing right and defense right, but also based on the necessity of legal defense, discipline in the trial and speedy judgment consideration, they are limited on the principle of immutability of litigation. This study tries to specify position of this principle in the Iranian civil procedure and American Federal law (Federal rules of Civil procedure), basics of the principle and identify its exceptions for its better execution.