United States v. Leon 468 U.S. 897, 104 S.Ct. 3405, 82 L.Ed.2d 677 (1984) The police had received a tip that Stewart and Sanchez were dealing drugs. They began watching who came to their house. Leon and DeCastillio were frequent visitors. Based on their frequent visits, and a tip from a second informant, the police got a judge to issue a search warrant. The search turned up a big pile of drugs and Leon and DelCastillo were arrested on suspicion of drug trafficking. At trial, Leon argued that the search was illegal because the anonymous tip and the surveillance were insufficient to create probable cause. Because the search warrant was held to have been invalid, all of the evidence stemming from that search warrant is inadmissible based on the exclusionary rule. The exclusionary rule basically says that illegally seized evidence should not be admissible as a policy, because it would deter law enforcement officials from obtaining evidence by any means necessary. The trial judge allowed the evidence to be admitted. Leon was convicted of drug trafficking. He appealed. The Appellate Court reversed and excluded all of the evidence based on the search warrant. The prosecution appealed. The US Supreme Court reversed and found that the evidence was admissible even though the search warrant was found to be deficient. The US Supreme Court found that evidence seized on the basis of an invalid search warrant was still admissible. As a matter of policy, the exclusionary rule doesn't have a deterrent effect if the police are acting in good faith and are following the rules to the best of their ability. Since the exclusionary rule is solely meant to deter illegal police conduct, not punish errors, it is not the right remedy for this situation. No matter what punishment is given, you can't deter honest mistakes. This case said that the exclusionary rule is there to be a deterrent, it is not there to be a remedy. The Court found that since letting obviously guilty people go free has a societal cost, and subverts the rule of law, on balance, the costs of the exclusionary rule outweigh the benefits in cases such as this. Turns out, if you look at the statistics, the costs are very small. Very few criminals are freed because of a successful motion to suppress based on a search and seizure violation. The Court also felt that since the job of the police is to catch criminals, they have a bias. However, the job of the magistrates who issue the warrants is to achieve justice, so they are more likely to be impartial. Therefore, if a magistrate issues a warrant, it is probably because he thinks it is the right thing to do. The assumption is that magistrates don't have the same anti-crime bias that the police do, but is that true? The basic rule is that unless a warrant is grounded upon an affidavit knowingly or recklessly false, evidence obtained pursuant to that warrant will be admissible. Aka the good faith exception. "The suppression of evidence obtained pursuant to a warrant should be ordered only on a case-by-case basis and only in those unusual cases in which exclusion will further the purposes of the exclusionary rule." Btw, the warrant has to be properly executed in order to qualify. This is an objective standard. The question that the judge must ask is not whether the particular policeman would know there was no probably cause, but whether a reasonable policeman would know that there was no probable cause. In a dissent it was argued that the judiciary was part of the whole process, and by the time the case reaches them they know that the warrant is not valid. Therefore, if they admit the evidence then they are acting on information they know to be false and are acting on an affidavit they know to be false. In a dissent it was argued that this decision would encourage the police to approach judges with only the minimum amount of information in future warrant applications, and reduce probable cause to not entirely unreasonable cause. Btw, the good faith exception only applies to situations where the police need a warrant. There are situations where the police need probable cause but not a warrant (like if they believe that someone is currently being attacked inside a house). In those cases, if the police are found to have been mistaken about the probable cause, they are not protected by the good faith exception.