United States v. Leon

The exclusionary rule should not apply to evidence obtained by officers acting in reasonable reliance on a search warrant issued by a detached and neutral magistrate. Reasonable minds frequently differ on whether a particular search warrant affidavit established probable cause. Officers are entitled to rely on the judgment of the issuing magistrate.

However, deference to a magistrate in search warrant matters is not boundless. A reviewing court’s deference to a finding of probable cause does not preclude its inquiry into the knowing or reckless falsity of the affidavit on which probable cause was based. A magistrate must perform a neutral and detached function and not serve merely as a rubber stamp for the government. Suppression is an appropriate remedy if information in an affidavit misled the issuing magistrate that the affiant knew was false or should have known was false (reckless disregard for the truth).