The adversarial system (or adversary system) of law is the system of law, generally adopted in common law countries, that relies on the skill of each advocate representing his or her party's positions and involves a neutral person, usually the judge, trying to determine the truth of the case. The inquisitorial system usually found on the continent of Europe among civil law systems (i.e., those deriving from Roman law or the Napoleonic Code) has a judge (or a group of judges who work together) whose task is to investigate the case. The adversarial system is the two-sided structure under which American criminal trial courts operate that pits the prosecution against the defense. Justice is done when the most effective adversary is able to convince the judge or jury that his or her perspective on the case is the correct one.