OCTOBER TERM, 2005
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, 337.
SUPREME COURT OF THE UNITED STATES
HUDSON v. MICHIGAN
CERTIORARI TO THE COURT OF APPEALS OF MICHIGAN
No. 04–1360. Argued January 9, 2006—Reargued May 18, 2006—
Decided June 15, 2006
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.
JUSTICE SCALIA delivered the opinion of the Court with respect to
Parts I, II,and III, concluding that violation of the “knock-andannounce” 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 theexclusionary rule, United States v. Leon, 468 U. S. 897, 908, 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, 363. 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-forcause, 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
HUDSON v. MICHIGANSyllabus
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 awarrant.
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 massiveremedy 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 thesesocial 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...