Mapp v. Ohio, decided in 1961 by the United States Supreme Court, established that US citizen (and non-citizen) criminal defendants could invoke an "exclusionary rule" to suppress evidence that was obtained through an illegal search, or a search done in violation of the Fourth Amendment to the US Constitution.
This marked the incorporation of the Fourth Amendment. In other words, while the exclusionary rule had previously applied to the federal government, Mapp v. Ohio extended its protections and restrictions to the states as well.
Two years later, in Wong v. United States, the court expanded the exclusionary rule with a corollary known as the "fruit of the poisonous tree" which set out that evidence subsequently gathered as an indirect result of an illegal search can also be excluded.
In Mapp v. Ohio (1961), the Supreme Court ruled that evidence obtained in violation of the Fourth Amendment's protection against unreasonable searches and seizures can't be used as evidence in state courts...
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