Why Courts Reject Illegally Obtained Evidence: New at Reason

Ever wondered why evidence is sometimes excluded during criminal trials?

In Weeks v. United States (1914), the U.S. Supreme Court announced a far-reaching doctrine known as the “exclusionary rule,” which generally bars the use in court of illegally obtained evidence.

Weeks arose after federal officials kicked down a criminal suspect’s door, scoured his home without a search warrant, and discovered various incriminating documents, which were later used against him at his federal trial. “If letters and private documents can thus be seized and held and used in evidence against a citizen accused of an offense,” the Court ruled, “the protection of the Fourth Amendment declaring his right to be secure against such [unreasonable] searches and seizures is of no value.”

In Mapp v. Ohio (1961), the Court extended the rule to criminal trials at the state level. “Presently, a federal prosecutor may make no use of evidence illegally seized,” the justices observed, “but a State’s attorney across the street may, although he supposedly is operating under the enforceable prohibitions of the same” Constitution, writes Damon Root.

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