The advantages of the adversary system include ensuring procedural law is strictly followed, having lawyers on both sides, preserving the right to privacy with the court working like a referee to ensure fairness and the defendant having the right to silence. The United States uses an adversary system.
The premise of the adversary system is to have an impartial person or persons, typically a judge or a jury, determine the truth after an advocate for each side presents the position of their party.
In criminal adversary proceedings, the defendant does not have to provide any evidence. However, if the defendant chooses to testify at trial, they can get a perjury charge and they are subject for cross-examination. This means that the representative of the opposing side can ask the defendant questions.
The defendant has the opportunity to provide a statement to the court. The opposing representative is not able to cross-examine this statement and the defendant is not under oath when they give this statement. This statement provides the defendant with the opportunity to tell their side of the story without anyone interfering and asking potentially incriminating questions.
Critics of the adversary system feel that it does not seek the truth, but that it only serves to resolve conflict. They also feel that the system puts more weight on winning than the truth.