United States v. Leon: Case Brief

Instructor: Anthony Rich

Anthony is currently a County Civil Prosecutor and has his Juris Doctorate. He has been a guest lecturer at several local universities.

United States. v. Leon was a federal drug trafficking criminal case. In this case, the Fourth Amendment exclusionary rule was changed to allow an exception. This exception allowed in evidence that was obtained in good faith by a police officer.


Police officers from the Burbank, California Police Department were conducting a drug-trafficking investigation. During their investigation they conducted surveillance of Alberto Leon and Richardo Del Castillo. The police officers also had a confidential informant who provided them with information. Based on their independent investigation and the confidential informant's information, they prepared a search warrant application for Leon's three residences and his automobiles. Part of this application included an affidavit, a written statement confirmed by oath, often used in court proceedings.

After the application was reviewed by several district attorneys, it was presented to a state court magistrate (and officer of the State, usually referred to as a judge) and signed by Officer Rombach. The state court magistrate then issued the search warrant. During the execution of the search warrant, large quantities of drugs and other evidence of Leon's criminal conduct was found.

At the trial court, in this case the district court, Leon's defense counsel filed a motion asserting that the affidavit of the search warrant was insufficient to establish probable cause for search warrant to be issued. The trial court sided with Leon's defense counsel, and the search warrant was invalid. They also concluded that although Officer Rombach acted in good faith, there was no 'good faith exception' (the police officer's belief that he was acting according to the law) to the Fourth Amendment's exclusionary rule, as the district attorneys attempted to argue.

This case was then brought to the Court of Appeals, affirmed, and finally appealed before the United States Supreme Court.


The issued presented before the U. S. Supreme Court was whether a 'good faith exception' to the Fourth Amendment's exclusionary rule should be recognized.


The U.S. Supreme Court determined that there should be an exception to the exclusionary rule of the Fourth Amendment. They held that when a police officer acts in a reasonable manner relying on a search warrant that was issued by a neutral magistrate, but ultimately found to be invalid, the evidence collected should not be barred from trial.


The U.S. Supreme Court examined the Fourth Amendment's origin and purpose when determining whether or not to impose exclusionary rule in this particular set of facts. They weighed the benefits and the costs of preventing the District Attorney's from using the inherently trustworthy and tangible evidence in their case in chief.

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