From colonial times, American courts have subscribed to the common law requirement that police, before using force to enter a private home, should knock and announce their identity and purpose. In Wilson v. Arkansas[c]Wilson v. Arkansas (1995), the Supreme Court explicitly affirmed that the Fourth Amendment incorporates this requirement, even though the ruling allowed exceptions for “exigent circumstances,” leaving it to the states to decide the details. In Richards v. Wisconsin[c]Richards v. Wisconsin (1997), the Court explained that a no-knock entry is justified when the police have a “reasonable suspicion” that announcing their presence would be dangerous or “inhibit the effectiveness” of police efforts. If the police were to conduct no-knock entries without adequate justification, however, any evidence obtained by the search would be suppressed according to the exclusionary rule.

In 1998, Detroit police officers obtained a regular warrant (with no exemption from the knock-and-announce rule) to search for drugs and weapons in the home of Booker T. Hudson. Without knocking, the officers announced their presence and waited only three or four seconds before entering through an unlocked door. They found guns and cocaine. At trial, Hudson’s lawyers argued that the evidence should be suppressed because the police had violated the knock-and-announce rule. Although agreeing that the rule had not been followed, the judge nevertheless allowed the evidence to be admitted, and Hudson was sentenced to eighteen months’ probation.

The U.S. Supreme Court voted five to four to uphold the conviction. Speaking for the majority, Justice Antonin ScaliaScalia, Antonin;Hudson v. Michigan acknowledged that the “knock-and-announce” rule was an ancient common law principle, but he argued that the suppression of evidence should be a last resort because “it generates substantial social costs which sometimes include setting the guilty free and the dangerous at large.” He further asserted that there was no causal connection between the constitutional violation (the failure to knock) and the discovery of evidence. The “increasing professionalism of the police,” moreover, minimized the need to deter misconduct. In a concurring opinion, Justice Anthony M. KennedyKennedy, Anthony M.;Hudson v. Michigan wrote that the Hudson ruling should be viewed narrowly, for it was not meant to diminish either the knock-and-announce principle or the exclusionary rule.

Speaking for the four-member minority, Justice Stephen BreyerBreyer, Stephen G.;Hudson v. Michigan wrote a heated dissent, charging that the majority had departed from the Court’s “basic principles” and had destroyed the major legal incentive of the police to comply with the knock-and-announce requirement. He took particular exception to Scalia’s causality argument for disregarding the exclusionary rule, which he wrote could make the Fourth Amendment unenforceable.

Breyer, Stephen G.

Common law

Kennedy, Anthony M.

Police powers

Scalia, Antonin

Search warrant requirement