Effects of Criminal Procedure on Crime Rates: Mapping Out the Consequences of the Exclusionary Rule

In 1961, in its Mapp v. Ohio ruling, the Supreme Court required every state to exclude from criminal trials evidence obtained in violation of the Fourth Amendment. This is the “exclusionary rule.” At the time the Supreme Court issued its ruling, 24 states allowed ill‐gotten evidence in their criminal trials, and 24 excluded it. An economic analysis of the search warrant process predicts an increase in crime rates after the Supreme Court forced states to adopt the exclusionary rule as police officers substitute away from searches toward alternatives they consider less effective. Our empirical analysis supports this theoretical prediction. We find a statistically and economically significant increase in crimes followed the Supreme Court’s imposition of the exclusionary rule, with suburban cities bearing the brunt of the Supreme Court's decision.