The Archive
Reference Library
The founding document as written, a plain overview of the seven Articles, and a glossary of archaic and legal terms.
Back to Supreme Court Rulings
Criminal Procedure
Mapp v. Ohio
Decided: 1961
In brief
Applied the Fourth Amendment exclusionary rule to the states, barring illegally obtained evidence from state trials.
The Court's ruling in depth
Cleveland police forced their way into Dollree Mapp's home without a valid warrant and found materials leading to an obscenity conviction. The Court held that evidence obtained in violation of the Fourth Amendment is inadmissible in state as well as federal courts. Mapp gave the exclusionary rule real teeth: without it, the Court reasoned, the Fourth Amendment would be 'a form of words.' It is a linchpin of the Warren Court's criminal-procedure revolution.