The New York Times' 2014 obituary for Mapp, describes how the case played out:
For more on the Mapp case, see The Cleveland Memory Project and the Marshall Project.
On May 23, 1957, three police officers arrived at a house in Cleveland and demanded to enter. They wanted to question a man about a recent bombing and believed he was hiding inside. A woman who lived there, Dollree Mapp, refused to admit them.
It was a small gesture of defiance that led to a landmark United States Supreme Court ruling on the limits of police power.
Ms. Mapp told the officers that she wanted to see a search warrant. They did not produce one. A few hours later, more officers arrived and forced their way into the house. Ms. Mapp called her lawyer and again asked to see a warrant. When one officer held up a piece of paper that he said was a warrant, Ms. Mapp snatched it and stuffed it into her blouse. The officer reached inside her clothing and snatched it back.
The officers handcuffed Ms. Mapp — they called her “belligerent” — and then searched her bedroom, where they paged through a photo album and personal papers. They also searched her young daughter’s room, the kitchen, a dining area and the basement.
They did not find the man they were looking for, but they did find what they said were sexually explicit materials — books and drawings that Ms. Mapp said had belonged to a previous boarder — and they arrested Ms. Mapp.
Four years later, after Ms. Mapp had been sentenced to prison on obscenity charges and after her conviction had been upheld on appeal, the Supreme Court took up the case, ostensibly because of questions it raised about obscenity and the First Amendment.
But when the justices ruled, in June 1961, their decision dwelled, with far more significant consequences, on the role of the Fourth Amendment, which protects against unlawful search and seizure. Prosecutors had never produced the supposed warrant brandished by the Cleveland police or proved that it had existed.
The court ruled, 6 to 3, that Ms. Mapp’s conviction should be thrown out, and that all state courts must suppress evidence gathered through police misconduct in certain kinds of cases.