Landmark Supreme Court Case · Rights of the accused
Mapp v. Ohio (1961)
- Decided
- 1961
- Vote
- 6–3
- Opinion
- Justice Tom C. Clark
- Constitutional provisions
Facts of the case
In 1957, Cleveland police came to Dollree Mapp's house looking for a bombing suspect. When she demanded a warrant, they forced their way in, waving a paper they claimed was a warrant (none was ever produced). They did not find the suspect, but they found allegedly obscene materials, and Mapp was convicted under Ohio law.
The constitutional question
May evidence obtained through an unconstitutional search be used in a state criminal trial?
The decision
No. The exclusionary rule, which says illegally obtained evidence cannot be used at trial, applies to the states through the 14th Amendment's Due Process Clause. (The Court had applied the rule to federal courts in Weeks v. United States, 1914.)
The Court's reasoning
Without the exclusionary rule, the Fourth Amendment's protection would be "a form of words," because police would have little incentive to obey it.
Why it matters
It incorporated the exclusionary rule against the states and changed police practices nationwide, a key moment in the Warren Court's "due process revolution." Later cases created exceptions, such as the good-faith exception (1984).