Which 1961 decision extended exclusionary rules of search and seizure to state court proceedings?

The 1961 decision that extended exclusionary rules of search and seizure to state court proceedings is Mapp v. Ohio. In this landmark ruling, the Supreme Court held that evidence obtained in violation of the Fourth Amendment cannot be used in state courts, thereby incorporating the exclusionary rule to apply to both federal and state prosecutions. This decision emphasized the importance of protecting individuals' constitutional rights against unlawful searches and seizures.