Dollree Mapp lived in a second-floor apartment in Cleveland. Police received a tip that someone wanted for questioning in a recent bombing case was hiding there. Without a search warrant, the officers went to the house and demanded entry. Mapp refused, telling the officers to get a warrant. The officers then forced entry.
During a search of the premises, officers found various items of pornography. Mapp was convicted of possession of obscene matter. She appealed to the Ohio Supreme Court, which ruled that even though it did appear the warrantless entry and search may have violated the Fourth Amendment, the federal exclusionary rule did not apply to state prosecutions. Therefore, the court affirmed the conviction. Mapp appealed to the U.S. Supreme Court.
A federal exclusionary rule had been created by the Supreme Court in the 1914 case of Weeks v. U.S., but this rule had been declared inapplicable to the states in Wolf v. Colorado, in 1949. Reversing Mapp's conviction, the U.S. Supreme Court voted 6 to 3 to overturn its own ruling in Wolf and impose the Fourth Amendment exclusionary rule on all of the states, via the Fourteenth Amendment due process clause.
In the words of the Mapp majority, "Since the Fourth Amendment's right of privacy has been declared enforceable against the States through the Due Process Clause of the Fourteenth, it is enforceable against them by the same sanction of exclusion as is used against the Federal
Government."
As a result of the ruling in Mapp, all states have procedures permitting a criminal defendant to move to suppress evidence claimed to have resulted from a violation of the Fourth Amendment. Many jurisdictions still use the terms "Mapp motion," "Mapp hearing," and "Mapp ruling" to refer to these procedures.