Which Supreme Court case applied the exclusionary rule to state courts?

Mapp v. Ohio applied the exclusionary rule to state courts. In 1961, the Supreme Court held that evidence obtained through an unconstitutional search or seizure could not be used in state criminal prosecutions.

The case began when Ohio police searched Dollree Mapp’s home while looking for a bombing suspect. They forced entry after displaying what officers claimed was a search warrant, but no valid warrant was produced in court. The search uncovered materials that led to Mapp’s conviction under an Ohio obscenity law.

Justice Tom C. Clark wrote the majority opinion. The Court relied on the Fourth Amendment’s protection against unreasonable searches and seizures and the Fourteenth Amendment’s application of that protection to the states. It overruled Wolf v. Colorado, which had recognized Fourth Amendment privacy rights but had not required states to exclude illegally obtained evidence.

Weeks v. United States had created the exclusionary rule for federal prosecutions in 1914, so it is a common distractor. Terry v. Ohio concerns stop-and-frisk, while Miranda v. Arizona concerns custodial interrogation and the right against self-incrimination.