An adversarial system is a type of legal system that is implemented within a jurisdiction. The United States employs the adversarial system within its area of sovereignty. This kind of system distinguishes 3 kinds of parties that participate in a process of litigation, whether it is criminal or civil law. The 3 parties involved are the plaintiff or prosecution, the defendant or defense, and the judge or jury.
The adversarial system makes use of an advocate to make an argument for a litigant in a court trial. The advocate is an attorney-at-law, or if the litigant wishes to make no use of a lawyer, it may be the litigant himself or herself who becomes his or her own advocate. Each advocate then presents arguments in favor of his or her side to an impartial individual or group of individuals in the form of judge or jury. This impartial party has the obligation to determine the truth of the matter from the arguments presented by each advocate and upon the presentation of evidence or testimony.
This kind of legal system is contrasted to an inquisitorial system wherein one individual or party investigates the claims made by opposing parties and determines what the truth is. The adversarial system is employed by most nations and states that espouse common law. The resolution of an adversarial system is based on which advocate was most convincing and proving of the truth. If no adversity is present in the matter, that is one party concedes to the other, then the matter is resolved.