United States v. Leon
Supreme Court of the United States
Argued January 17, 1984 Decided July 5, 1984
Full case name	United States v. Leon et al.
Citations	468 U.S. 897 (more)
Prior history	Certiorari to the United States Court of Appeal for the Ninth Circuit.
Subsequent history	701 F.2d 187, reversed.
Holding
Established that evidence obtained in good faith by police relying upon a search warrant that subsequently is found to be deficient may be used in a criminal trial.
Court membership
Chief Justice Warren E. Burger     Associate Justices William J. Brennan, Jr. · Byron White Thurgood Marshall · Harry Blackmun Lewis F. Powell, Jr. ·William Rehnquist John P. Stevens · Sandra Day O'Connor
Case opinions
Majority	White, joined by Burger, Blackmun, Powell, Rehnquist, O'Connor
Dissent	Brennan, joined by Marshall, Stevens
Laws applied
U.S. Const. amend. IV

United States v. Leon, 468 U.S. 897 (1984)[1], was a search and seizure case in which the Supreme Court of the United States created the "good faith" exception to the exclusionary rule.

Background
In August 1981, police in Burbank, California received a tip identifying Patsy Stewart and Armando Sanchez as drug dealers. Police began surveillance of their homes and followed leads based on the cars that frequented the residences. The police identified Ricardo Del Castillo and Alberto Leon as also being involved in the operation. Based on this surveillance and information from a second informant, a detective wrote an affidavit and a judge issued a search warrant. The police conducted the search, but the search warrant was later found to be invalid because the police lacked the probable cause for a warrant to be issued in the first place. The evidence obtained in the search was upheld anyway, because the police performed the search in reliance on the warrant, meaning they acted in good faith. This became known as the good faith exception to the exclusionary rule.

Arguments
Exclusion of evidence obtained by the police in violation of the Fourth Amendment was made applicable to individual states in Mapp v. Ohio (1961). Theexclusionary rule, which forbids the use of evidence obtained through illegal search in a criminal trial, is "neither intended nor able to 'cure the invasion of the defendant's rights which he has already suffered.'" Justice Byron White states that the Court has previously defined the limits of the exclusionary rule and that there is therefore good reason to do so in this case. The exclusionary rule was designed to deter unlawful police action, not punish the errors of magistrates. There is no evidence that judges and magistrates are more likely to ignore suspects' Fourth Amendment rights. White also states that there is no evidence that the exclusion of evidence will deter magistrates from issuing unsound warrants.

White clarifies that suppression of evidence should continue in cases where the magistrate was misled by information supplied in an affidavit in "bad faith". As long as the person writing the affidavit wrote it in good faith, the decision is that of the magistrate and the exclusionary rule serves no useful function. The officers enforcing the warrant must be able to rely on the decision of the magistrate..