United States v. Leon, 468 U.S. 897 (1984)

The Fourth Amendment prohibits governmental officials from carrying out unreasonable searches and seizures. Under the Fourth Amendment exclusionary rule, evidence obtained by the government from an unconstitutional search will normally be excluded at the criminal trial.

In its landmark decision in Mapp v. Ohio (1961), the Supreme Court held that the Fourth Amendment exclusionary rule applies in state criminal proceedings. The Court in Mapp found that the exclusionary rule is necessary to deter police violations of the Fourth Amendment. The decision in Mapp generated intense controversy and debate. In United States v. Leon (1984), the Supreme Court created a significant exception to the exclusionary rule. Under Leon, if a law enforcement officer conducts a search in good faith reliance on a search warrant issued by a magistrate that is not based on probable cause, the exclusionary rule does not apply. An officer acts in good faith when reliance on the warrant is objectively reasonable. In the companion case of Massachusetts v. Sheppard (1984), the Court held that the Leon good-faith exception also applies when the warrant fails to describe the place to be searched with sufficient particularity.

The Court’s opinion in Leon reads like a brief against the exclusionary rule. The Court adopted the view that the exclusionary rule is not mandated by the Fourth Amendment but is merely a judicially created remedy. Furthermore, there is great cost in applying the rule in that it impedes the truth-finding function and allows some guilty defendants to go free. As Justice Cardozo famously put it, the ‘‘criminal is to go free because the constable has blundered.’’ On the ‘‘benefit’’ side of the cost–benefit analysis, the Court found no empirical evidence to support the deterrence rationale behind the exclusionary rule. To the extent deterrence supports the rule, it is designed to deter Fourth Amendment violations by law enforcement officers, not by magistrates.

The decision in Leon states that the good-faith exception does not apply when (1) the police officer did not have an objectively reasonable belief that the warrant was supported by probable cause; (2) the warrant was based on a police officer’s affidavit that knowingly or recklessly omitted or misstated material facts; (3) the execution of the warrant was unreasonable; or (4) the magistrate wholly abandoned his or her role as a neutral and detached magistrate, for example, by either ‘‘rubber stamping’’ police applications for warrants or by participating in the search.

The actual impact of Leon on the police and criminal prosecutions has probably not been great, because most searches are conducted without a warrant, for example, incident to a lawful arrest or with consent. Nevertheless, the decision is important because it revealed the Supreme Court’s distinctively negative attitude toward the exclusionary rule. Applying the rationale of Leon, the Court later held that the exclusionary rule does not apply when the officer’s search was based on his good faith reliance on a state statute later declared unconstitutional, Illinois v. Krull (1987) or on inaccurate law enforcement records attributable to an error by a court employee (Arizona v. Evans, 1995).

MARTIN A. SCHWARTZ

References and Further Reading

  • LaFave, W., J. Israel, and N. King. Criminal Procedure. 4th ed. 2004.

Cases and Statutes Cited

  • Arizona v. Evans, 514 U.S. 1 (1995)
  • Illinois v. Krull, 480 U.S. 340 (1987)
  • Mapp v. Ohio, 367 U.S. 643 (1961)
  • Massachusetts v. Sheppard, 468 U.S. 981 (1984)
  • United States v. Leon, 468 U.S. 897 (1984)
  • Weeks v. United States, 232 U.S. 383 (1914)
  • Wolf v. Colorado, 338 U.S. 25 (1949)

See also Bivens v. Six Unknown Named Agents, 403 U.S. 388 (1971); Exclusionary Rule; Probable Cause; Warrantless Searches

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