Syllabus

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued.The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader.See United States v. Detroit Timber & Lumber Co., 200 U. S. 321 .

HUDSON v. MICHIGAN

certiorari to the court of appeals of michigan

---

---

Detroit police executing a search warrant for narcotics and weapons entered petitioner Hudson’s home in violation of the Fourth Amendment ’s “knock-and-announce” rule. The trial court granted Hudson’s motion to suppress the evidence seized, but the Michigan Court of Appeals reversed on interlocutory appeal. Hudson was convicted of drug possession. Affirming, the State Court of Appeals rejected Hudson’s renewed Fourth Amendment claim.

Held: The judgment is affirmed.

Affirmed.

Justice Scalia delivered the opinion of the Court with respect to Parts I, II, and III, concluding that violation of the “knock-and-announce” rule does not require suppression of evidence found in a search. Pp. 2–13.

(a) Because Michigan has conceded that the entry here was a knock-and-announce violation, the only issue is whether the exclusionary rule is appropriate for such a violation. Pp. 2–3.

(b) This Court has rejected “[i]ndiscriminate application” of the exclusionary rule, United States v. Leon, 468 U. S. 897 , holding it applicable only “where its deterrence benefits outweigh its ‘substantial social costs,’ ” Pennsylvania Bd. of Probation and Parole v. Scott, 524 U. S. 357 . Exclusion may not be premised on the mere fact that a constitutional violation was a “but-for” cause of obtaining the evidence. The illegal entry here was not the but-for cause, but even if it were, but-for causation can be too attenuated to justify exclusion. Attenuation can occur not only when the causal connection is remote, but also when suppression would not serve the interest protected by the constitutional guarantee violated. The interests protected by the knock-and-announce rule include human life and limb (because an unannounced entry may provoke violence from a surprised resident), property (because citizens presumably would open the door upon an announcement, whereas a forcible entry may destroy it), and privacy and dignity of the sort that can be offended by a sudden entrance. But the rule has never protected one’s interest in preventing the government from seeing or taking evidence described in a warrant. Since the interests violated here have nothing to do with the seizure of the evidence, the exclusionary rule is inapplicable. Pp. 3–7.

(c) The social costs to be weighed against deterrence are considerable here. In addition to the grave adverse consequence that excluding relevant incriminating evidence always entails—the risk of releasing dangerous criminals—imposing such a massive remedy would generate a constant flood of alleged failures to observe the rule, and claims that any asserted justification for a no-knock entry had inadequate support. Another consequence would be police officers’ refraining from timely entry after knocking and announcing, producing preventable violence against the officers in some cases, and the destruction of evidence in others. Next to these social costs are the deterrence benefits. The value of deterrence depends on the strength of the incentive to commit the forbidden act. That incentive is minimal here, where ignoring knock-and-announce can realistically be expected to achieve nothing but the prevention of evidence destruction and avoidance of life-threatening resistance, dangers which suspend the requirement when there is “reasonable suspicion” that they exist, Richards v. Wisconsin, 520 U. S. 385 . Massive deterrence is hardly necessary. Contrary to Hudson’s argument that without suppression there will be no deterrence, many forms of police misconduct are deterred by civil-rights suits, and by the consequences of increasing professionalism of police forces, including a new emphasis on internal police discipline. Pp. 8–13.

Justice Scalia, joined by The Chief Justice, Justice Thomas, and Justice Alito, concluded in Part IV that Segura v. United States, 468 U. S. 796 , New York v. Harris, 495 U. S. 14 , and United States v. Ramirez, 523 U. S. 65 , confirm the conclusion that suppression is unwarranted in this case. Pp. 13–16.

Scalia, J., delivered the opinion of the Court with respect to Parts I, II, and III, in which Roberts, C. J.,and Kennedy, Thomas, and Alito, JJ., joined, and an opinion with respect to Part IV, in which Roberts, C. J., and Thomas and Alito, JJ., joined. Kennedy, J., filed an opinion concurring in part and concurring in the judgment. Breyer, J., filed a dissenting opinion, in which Stevens, Souter, and Ginsburg, JJ., joined.