Which case established the exclusionary rule in the United States?

The establishment of the exclusionary rule in the United States is chiefly attributed to the landmark case of Mapp v. Ohio. This case addressed the issue of illegal searches and seizures and reinforced the application of the Fourth Amendment at the state level. Prior to Mapp, the exclusionary rule, which prevents the government from using evidence obtained in violation of the Constitution, was primarily enforced in federal cases.

Through Mapp v. Ohio, the Supreme Court ruled that evidence obtained through unconstitutional searches and seizures by state officials cannot be used in state courts. This ruling effectively nationalized the exclusionary rule, ensuring that all states are required to adhere to the standards set by the Fourth Amendment. The decision was pivotal in protecting individual rights and ensuring law enforcement conducted searches in a lawful manner, reinforcing the principle that illegally obtained evidence undermines the integrity of the judicial process.

Other cases mentioned address different aspects of legal rights and law enforcement procedures. For example, Miranda v. Arizona deals with the rights of the accused during police interrogations, Gideon v. Wainwright ensures the right to counsel for defendants, and Terry v. Ohio pertains to stop-and-frisk procedures, but none specifically established the exclusionary rule as Mapp v. Ohio did.