Beyond Standards of Proof: Accuracy and Frugality of Different Legal Systems

Different standards of proof are applied under the common law systems and the civil law systems. The reason is that the common-law adversarial systems rely on litigating parties to produce evidence while the civil-law inquisitorial systems rely on impartial judges to produce evidence, so the collections of evidence presented to the court are largely different. This paper analyzes the adversarial system with its preponderance of the evidence standard and the inquisitorial system with its theoretical optimal standard of proof. Specifically, we model the adversarial litigation as an evidence presentation game in which the two parties produce and present evidence to the court to maximize their expected payoffs. The equilibrium shows that this system may not be the most accurate fact-finding system. In contrast, the inquisitorial factfinding, which is analyzed analogously as a statistical hypothesis testing problem, may be more accurate. However, the advantage of the adversarial system is that, it deters more frivolous litigations and encourages more settlements, so it is more frugal because of the considerable litigation resources it saves. * The author is grateful to Professor Vincy Fon for helpful research comments on this paper. All omissions and errors are the author’s sole responsibility.