Mapp v. Ohio

The Court held that evidence obtained through unconstitutional searches is inadmissible in state criminal trials.

Overview

Cleveland police forced their way into Dollree Mapp's home without a valid warrant, allegedly searching for a bombing suspect, and seized obscene materials. The Court held that the Fourth Amendment exclusionary rule applies to the states through the Fourteenth Amendment, overruling Wolf v. Colorado. The reasoning was that excluding illegally seized evidence was the only effective deterrent against police lawlessness. Mapp nationalized the exclusionary rule, transformed everyday police practices, and remains a bedrock of American criminal procedure, though exceptions for good faith and other circumstances have multiplied in later decades.