How did United States v. Leon create a good-faith exception to the exclusionary rule?

In United States v. Leon (1984), the U.S. Supreme Court established the "good-faith" exception to the exclusionary rule, which generally prohibits the use of evidence seized in violation of the Fourth Amendment at trial.12

The Court determined that evidence obtained by police officers acting in "good faith"—specifically when they rely on a search warrant that is later found to be technically invalid—should remain admissible. The ruling was driven by the concern that the "social cost" of excluding reliable evidence, which could otherwise secure a conviction, was unacceptably high when the police had made an honest mistake while attempting to comply with constitutional requirements.12

By allowing this exception, the Court shifted the focus toward the conduct of the police, reasoning that the exclusionary rule’s primary purpose is to deter police misconduct rather than to punish errors made by judges or magistrates in the warrant-issuing process.12