MAPP V. OHIO, decided on 20 June 1961, was a landmark court case originating in Cleveland, in which the U.S. Supreme Court ruled that under the 4th and 14th Constitutional amendments, illegally seized evidence could not be used in a state criminal trial. This decision significantly changed state law-enforcement procedures throughout the country. The case began on 23 May 1957 when police officers entered the Cleveland home of Dollree Mapp looking for a person wanted for questioning in a recent bombing and seeking illegal gambling paraphernalia. After a thorough search, the police found neither the person nor the gambling materials. However, they did find obscene material, which Mapp denied owning. Possession of obscene materials was then illegal according to state law, and Mapp was arrested. In the fall of 1958, she was tried, convicted, and sentenced to 1-7 years in the penitentiary. No search warrant was produced at the trial, nor was the failure to produce one accounted for. Mapp's lawyer, Alexander L. Kearns, appealed to the Ohio Supreme Court on the basis that Ohio's obscenity law violated the right to privacy, and only secondarily that the conduct of the police in obtaining the evidence was unconstitutional. The court affirmed the conviction, and despite the absence of a search warrant, also ruled that illegally seized evidence could be entered in a criminal trial.
Kearns appealed the case to the U.S. Supreme Court, contending that Mapp's conviction violated her constitutional rights. At the invitation of the Court, Cleveland attorney Bernard A. Berkman, representing the American Civil Liberties Union, also submitted a brief. During the oral argument, he urged the high court to examine the constitutionality of search-and-seizure usage in state courts, since federal courts prohibited the use of illegally obtained evidence. The Supreme Court's 5-4 decision overturned Mapp's conviction, on the grounds that evidence seized without a search warrant cannot be used in state criminal prosecutions under the 4th Amendment to the Constitution, which protects against unreasonable searches and seizures, and the 14th Amendment, which extends that protection to state jurisdictions.