What distinguishes an "adversarial" system from an "inquisitorial" system?

The distinguishing feature of an adversarial system compared to an inquisitorial system lies in the roles of the opposing parties and the judge. In an adversarial system, which is commonly found in countries like the United States, the legal process is characterized by two opposing sides: the prosecution and the defense. Each party presents its case and argues against the other, with an impartial judge overseeing the proceedings to ensure fairness and adherence to the law. The judge does not take an active role in investigating the case or gathering evidence; instead, they serve primarily as a referee between the two sides.

In contrast, an inquisitorial system, commonly seen in many European countries, involves a more active role for the judge, who may investigate the facts, question witnesses, and gather evidence. The judge plays a significant role in steering the proceedings, which differs fundamentally from the adversarial approach where the parties drive the case.

This foundational structural difference in how cases are presented and managed forms the basis of the distinction between the two systems.