Mapp v. Ohio was a 1961 landmark Supreme Court case decided 6–3 by the Warren Court, in which it was held that Fourth Amendment’s protection against unreasonable searches and seizures applied to the states and excluded unconstitutionally obtained evidence from use in state criminal prosecutions. This decision overruled Wolf v. Colorado and reversed the conviction of appellant Dollree Mapp.
Dollree Mapp’s home in Cleveland, Ohio was forcefully entered by police officers who believed that a suspected bomber was inside the house. While searching her home, officers found pornographic books. Later, Mapp was prosecuted under an Ohio statute for knowing possession of lewd and lascivious material. She was convicted even though the prosecution was unable to produce a valid search warrant.
The majority held that all evidence obtained unconstitutionally, without a search warrant, is inadmissible in state criminal prosecutions. Such evidence was already barred in federal courts, but the majority agreed that the exclusionary rule for unlawfully seized evidence applied to state courts as well, through the Fourteenth Amendment. The Supreme Court insisted that the exclusionary rule had to apply to the states, or else the Fourth Amendment was essentially useless.
[Last updated in June of 2020 by the Wex Definitions Team]