The courts
exclusionary rule
Evidence obtained by violating the Constitution generally cannot be used against the defendant. The remedy that gives the Fourth Amendment practical teeth.
In full
Mapp v. Ohio (1961) applied the rule to the states. Its rationale is deterrence rather than personal remedy, which is why the Court has carved out exceptions: good faith reliance on a defective warrant, inevitable discovery, and attenuation. Fruit of the poisonous tree extends exclusion to evidence derived from the original violation.
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A plain-language explanation for civic education, not legal advice. When in doubt, the official source named above controls.