Better that X guilty persons escape than that one innocent suffer

The principle that it is better to let some guilty individuals be set free than to mistakenly convict an innocent person is generally shared by legal scholars, judges and lawmakers of modern societies. The paper shows why this common trait of criminal procedure is also efficient. It extends the standard Polinsky and Shavell (2007) model of deterrence and shows that when the costs of convictions are positive, and guilty individuals are more likely to be convicted than innocent individuals it is always efficient to minimize the number of wrongful convictions, while a more than minimal amount of wrongful acquittals may be optimal.