Knock-and-announce

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Knock-and-announce, in United States law criminal procedure, is an ancient common law principle, incorporated into the Fourth Amendment,^[1] which requires law enforcement officers to announce their presence and provide residents with an opportunity to open the door prior to a search.

The rule is currently codified in the United States Code,^[2] which governs Fourth Amendment searches conducted by the federal government. Most states have similarly codified the rule into their own statutes,^[3] and remain free to interpret or augment the rule and its consequences in any fashion that remains consistent with Fourth Amendment principles.^[4] A state's knock-and-announce rule will govern searches by state actors pursuant to state-issued warrants, assuming that Federal actors are not extensively involved in the search.