United States v. Leon
The Supreme Court ruled that evidence police gather while reasonably relying on a search warrant later found invalid can still be used at trial, creating a new "good faith" exception to the exclusionary rule.
The decision marks the first time the Court has allowed illegally obtained evidence into a criminal trial's case in chief against the very person whose rights were violated, reshaping decades of Fourth Amendment practice.
“We conclude that the marginal or nonexistent benefits produced by suppressing evidence obtained in objectively reasonable reliance on a subsequently invalidated search warrant cannot justify the substantial costs of exclusion.”
The Court's central holding creating the good-faith exception.
How it got here: A federal trial court suppressed evidence for lack of probable cause; the Ninth Circuit affirmed and declined to adopt a good-faith exception; the government asked the Supreme Court to create one.
The Case in Depth
What happened
Burbank police investigated several people suspected of large-scale drug trafficking based partly on a tip from an unproven informant. Officers got a search warrant from a state judge and found drugs at multiple homes and in cars. The defendants argued the informant's information was too old and unverified to establish probable cause, and moved to suppress the evidence found in the searches.
The question before the Court
If police search a home using a warrant a judge approved, but the warrant later turns out to have been issued without enough evidence, can prosecutors still use what they found?
Why it matters
Police who honestly and reasonably rely on a judge-approved warrant no longer risk having evidence thrown out just because the warrant is later found defective. That gives law enforcement more confidence to seek warrants, while critics warn magistrates and officers may now have less incentive to scrutinize warrant applications carefully.
What changes now
The judgment of the Ninth Circuit is reversed, meaning the previously suppressed evidence can now be used against the defendants at trial. The case does not disturb the underlying probable-cause standard or warrant requirements — it only changes what happens when a warrant later turns out to be invalid. Lower courts going forward must apply the new good-faith test whenever defendants seek to suppress evidence gathered under a warrant.
What this does not decide
The Court did not lower the probable-cause standard or change what a valid warrant requires; it addressed only the remedy when a warrant later proves invalid. The good-faith exception does not apply if officers lied to get the warrant, the magistrate abandoned neutrality, the affidavit was so thin it gave no real basis for probable cause, or the warrant was obviously deficient on its face.
Concurrences and dissents
Concurrence — Justice Blackmun
Justice Blackmun joined the majority but stressed that the ruling rests on an untested empirical guess about how the good-faith exception will affect police behavior. He emphasized the decision is provisional and that the Court should revisit it if real-world experience shows the exception undermines compliance with the Fourth Amendment.
Dissent — Justice Brennan
Justice Brennan argued the exclusionary rule is not merely a deterrence tool but a constitutional command flowing directly from the Fourth Amendment itself, so courts that admit illegally obtained evidence become complicit in the constitutional violation. He contended the majority's cost-benefit analysis is unreliable, understates the rule's institutional deterrent value, and would encourage magistrates and police to grow careless in seeking and issuing warrants.
Concurrence in part — Justice Stevens
Justice Stevens agreed with the outcome in the companion case (Massachusetts v. Sheppard) but dissented here, arguing the Court should have first decided whether the warrant actually violated the Fourth Amendment rather than reaching for a broad new exception. He also argued a search cannot logically be both constitutionally unreasonable and reasonable at the same time, and that the good-faith exception undermines incentives for police and magistrates to comply carefully with the Fourth Amendment.
How the Court got there
The legal reasoning, step by step
- The Court framed the exclusionary rule — the doctrine barring illegally obtained evidence from trial — not as a personal constitutional right but as a judge-made remedy meant only to deter police misconduct, weighing its costs against its deterrent benefits case by case.
- Applying that cost-benefit framework, the Court reasoned that excluding evidence only makes sense where doing so would actually change police behavior going forward.
- The Court found that when officers reasonably rely on a warrant a neutral judge has already approved, there is essentially no police misconduct to deter, because the officers followed the correct process and it was the magistrate, not the police, who may have erred.
- Because magistrates are not the police and have no stake in prosecutions, the Court concluded that excluding evidence in these cases would not meaningfully improve how magistrates screen warrant applications either.
- The Court therefore created a good-faith exception: evidence seized under a warrant later found invalid is still admissible if a reasonably well-trained officer would have believed the warrant was valid, unless the affidavit was knowingly or recklessly false, the magistrate abandoned a neutral role, the affidavit was a bare-bones recitation lacking any real basis for probable cause, or the warrant was facially deficient.
- Measured against that standard, the Court concluded the officers' reliance on the warrant here was objectively reasonable, since the underlying affidavit reflected an extensive investigation even though it ultimately fell short of probable cause.
Doctrinal impact
Cases affected by this decision
Limits Mapp v. Ohio (367 U.S. 643)
The Court narrows Mapp's broad exclusionary-rule requirement by carving out a good-faith exception for warrant-based searches.