Mapp v. Ohio

After Mapp, state police as well as state courts, where most criminal prosecutions take place, were obliged to follow the Fourth Amendment prohibition against illegal search and seizure.

On 23 May 1957, officers from the Cleveland, Ohio, police department came to the home of Dollree Mapp, seeking entry. They had information that a person wanted for questioning in connection with a bombing was hiding inside. They also believed that the house contained gambling equipment. After calling her lawyer, Mapp refused to let them in without a warrant.

Police continued to watch the house. Three hours later, they again sought entrance. When Mapp did not immediately come to the door, they forced their way inside. Meanwhile, Mapp's lawyer had arrived, but the police, who had begun to search the premises, would not let him in and would not allow him to see his client. Encountering officers on the stairs, Mapp again demanded to see a warrant. She was shown a piece of paper (not a warrant), which she grabbed. She struggled as police tried to retrieve it, and as a result she was handcuffed because she had been "resisting arrest."

Police never did find what they supposedly were looking for, but in the course of their search they happened across some allegedly obscene books and photographs. Mapp was convicted of possessing obscene material and put in prison. The Ohio Supreme Court upheld her conviction, even while conceding that the search that had netted the evidence used against her was "unlawful." The state's highest court concluded that the evidence could be used against Mapp because of a 1949 U.S. Supreme Court ruling, Wolf v. People of the State of Colorado. Although in Wolf the Court ruled that states are bound by the due process requirements of the Fourth Amendment, the majority opinion in that case also stated that the exclusionary rule--preventing improperly obtained evidence from being introduced in court--need not be applied in state court proceedings.

When Mapp took her case to the U.S. Supreme Court, her lawyers appealed her conviction primarily on First Amendment grounds. They argued that the state of Ohio had violated Mapp's right to freedom of thought and expression by making the mere possession of obscene material illegal. However, the American Civil Liberties Union also filed an amicus ("friend of the court") brief in which it argued for a reconsideration of Wolf.