Dollree Mapp was convicted of possessing obscene materials after an admittedly illegal police search of her home for a fugitive. She appealed her conviction on the basis of freedom of expression.

Were the confiscated materials protected by the First Amendment? (May evidence obtained through a search in violation of the Fourth Amendment be admitted in a state criminal proceeding?)

The Court brushed aside the First Amendment issue and declared that "all evidence obtained by searches and seizures in violation of the Constitution is, by [the Fourth Amendment], inadmissible in a state court." Mapp had been convicted on the basis of illegally obtained evidence. This was an historic -- and controversial -- decision. It placed the requirement of excluding illegally obtained evidence from court at all levels of the government. The decision launched the Court on a troubled course of determining how and when to apply the exclusionary rule.

Source

• http://www.oyez.org/cases/1960-1969/1960/1960_236#sort=ideology