468 U.S. 897 (1984), argued 17 Jan. 1984, decided 5 July 1984 by vote of 6 to 3; White for the Court, Blackmun concurring, Brennan, Marshall, and Stevens in dissent. In Leon, the Court heard arguments regarding whether it should create a broad exception to the Fourth Amendment's exclusionary rule for good-faith police mistakes. The Court did create an exception to the rule that allows evidence seized in almost all searches conducted pursuant to unconstitutional warrants to be used without restriction in criminal prosecutions. Notwithstanding that it is frequently labeled as “the good-faith exception,” however, the Leon exception is actually more limited in scope, and based on a different rationale, than the broad exception that had been proposed.
The idea for a good-faith exception came from critics of the exclusionary rule, who asserted that many unconstitutional searches were made simply because the police made honest mistakes about confusing search rules. These critics also argued, applying the deterrence rationale for the exclusionary rule adopted in United States v. Calandra (1974), that suppressing evidence that was seized unconstitutionally because of honest police mistakes served no purpose because the police could not be deterred from future unconstitutional searches if they had acted by mistake. Thus, the critics proposed that unconstitutionally seized evidence should be admissible in criminal trials whenever the police had acted because of a good-faith, albeit mistaken, belief that the search was constitutional.
Defenders of the exclusionary rule opposed the proposed exception on the ground that unconstitutionally seized evidence should be suppressed as a matter of principle to enforce Fourth Amendment rights and to protect the integrity of the courts. They also expressed doubt that honest mistakes are a frequent cause of illegal searches and argued that there is no reason to think that suppression of evidence would be less likely to deter future police misconduct just because the police had made a mistake. Defenders of the rule also questioned whether courts could reliably distinguish between mistaken and willful unconstitutional searches and, as a result, voiced concern that any good-faith mistake exception would be so open-ended in practice that it would effectively end enforcement of Fourth Amendment search standards.
Although Justice Byron White's majority opinion is clearly influenced by the proposal for a broad good-faith exception, the Leon exception is more limited in both its scope and its rationale. With regard to its scope, the Leon exception is explicitly limited to searches for which the police have obtained a search warrant that is later ruled to be invalid. Most police searches are, however, conducted without search warrants. Thus, as a practical matter, it is doubtful that the Leon exception will affect evidence in many cases, especially because search warrants were rarely found to be invalid even prior to Leon.
With regard to Leon's rationale, White did not discuss police “good faith” generally but justified the exception on the narrow premise that the police should not be asked to second guess the validity of a judge's decision to issue a search warrant. He asserted that the exclusionary rule was only designed to reach police misconduct, not judicial errors; hence, he concluded that the rule should not apply to an invalid search warrant that is the fault of a judge rather than the police. Because of this narrow rationale, it is questionable whether Leon should be viewed as precedent for a broad good-faith exception that would apply to unconstitutional warrantless searches. Nevertheless, Leon is a significant development because it is the first decision to find a Fourth Amendment violation but nevertheless allow unrestricted use of unconstitutionally seized evidence in criminal proceedings, including the prosecution's case-in-chief at trial. At least implicitly, Leon appears to embrace the proposition that there need not be any recourse or remedy available to victims of Fourth Amendment violations.