Hudson v. Michigan

(Slip Opinion) OCTOBER TERM, 2005 1

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, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

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 Amend
ment’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 Hud
son’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 exclu
sionary rule is appropriate for such a violation. Pp. 2–3.
(b) This Court has rejected “[i]ndiscriminate application” of the ex
clusionary rule, United States v. Leon, 468 U. S. 897, 908, holding it
applicable only “where its deterrence benefits outweigh its ‘substan
tial 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-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
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Syllabus

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 gov
ernment 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 consider
able here. In addition to the grave adverse consequence that exclud
ing relevant incriminating evidence always entails—the risk of re
leasing 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 inade
quate support. Another consequence would be police officers’ refrain
ing from timely entry after knocking and announcing, producing pre
ventable 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 mini
mal here, where ignoring knock-and-announce can realistically be
expected to achieve nothing but the prevention of evidence destruc
tion and avoidance of life-threatening resistance, dangers which sus
pend the requirement when there is “reasonable suspicion” that they
exist, Richards v. Wisconsin, 520 U. S. 385, 394. Massive deterrence
is hardly necessary. Contrary to Hudson’s argument that without
suppression there will be no deterrence, many forms of police mis
conduct 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.
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Opinion of the Court

NOTICE: This opinion is subject to formal revision before publication in the
preliminary print of the United States Reports. Readers are requested to
notify the Reporter of Decisions, Supreme Court of the United States, Wash
ington, D. C. 20543, of any typographical or other formal errors, in order
that corrections may be made before the preliminary print goes to press.

SUPREME COURT OF THE UNITED STATES
_________________

No. 04–1360
_________________

BOOKER T. HUDSON, JR., PETITIONER v. MICHIGAN
ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF

MICHIGAN

[June 15, 2006]

JUSTICE SCALIA delivered the opinion of the Court,
except as to Part IV.
We decide whether violation of the “knock-and
announce” rule requires the suppression of all evidence
found in the search.
I
Police obtained a warrant authorizing a search for drugs
and firearms at the home of petitioner Booker Hudson.
They discovered both. Large quantities of drugs were
found, including cocaine rocks in Hudson’s pocket. A
loaded gun was lodged between the cushion and armrest of
the chair in which he was sitting. Hudson was charged
under Michigan law with unlawful drug and firearm
possession.
This case is before us only because of the method of
entry into the house. When the police arrived to execute
the warrant, they announced their presence, but waited
only a short time—perhaps “three to five seconds,” App.
15—before turning the knob of the unlocked front door
and entering Hudson’s home. Hudson moved to suppress
all the inculpatory evidence, arguing that the premature
entry violated his Fourth Amendment rights.
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Opinion of the Court

The Michigan trial court granted his motion. On inter
locutory review, the Michigan Court of Appeals reversed,
relying on Michigan Supreme Court cases holding that
suppression is inappropriate when entry is made pursuant
to warrant but without proper “ ‘knock and announce.’ ”
App. to Pet. for Cert. 4 (citing People v. Vasquez, 461 Mich.
235, 602 N. W. 2d 376 (1999) (per curiam); People v. Ste
vens, 460 Mich. 626, 597 N. W. 2d 53 (1999)). The Michi
gan Supreme Court denied leave to appeal. 465 Mich.
932, 639 N. E. 2d 255 (2001). Hudson was convicted of
drug possession. He renewed his Fourth Amendment
claim on appeal, but the Court of Appeals rejected it and
affirmed the conviction. App. to Pet. for Cert. 1–2. The
Michigan Supreme Court again declined review. 472
Mich. 862, 692 N. W. 2d 385 (2005). We granted certio
rari. 545 U. S. ___ (2005).
II
The common-law principle that law enforcement officers
must announce their presence and provide residents an
opportunity to open the door is an ancient one. See Wilson
v. Arkansas, 514 U. S. 927, 931–932 (1995). Since 1917,
when Congress passed the Espionage Act, this traditional
protection has been part of federal statutory law, see 40
Stat. 229, and is currently codified at 18 U. S. C. §3109. We
applied that statute in Miller v. United States, 357 U. S. 301
(1958), and again in Sabbath v. United States, 391 U. S. 585
(1968). Finally, in Wilson, we were asked whether the rule
was also a command of the Fourth Amendment. Tracing its
origins in our English legal heritage, 514 U. S., at 931–936,
we concluded that it was.
We recognized that the new constitutional rule we had
announced is not easily applied. Wilson and cases follow
ing it have noted the many situations in which it is not
necessary to knock and announce. It is not necessary
when “circumstances presen[t] a threat of physical vio
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Opinion of the Court

lence,” or if there is “reason to believe that evidence would
likely be destroyed if advance notice were given,” id., at
936, or if knocking and announcing would be “futile,”
Richards v. Wisconsin, 520 U. S. 385, 394 (1997). We re
quire only that police “have a reasonable suspicion . . . under
the particular circumstances” that one of these grounds for
failing to knock and announce exists, and we have acknowl
edged that “[t]his showing is not high.” Ibid.
When the knock-and-announce rule does apply, it is not
easy to determine precisely what officers must do. How
many seconds’ wait are too few? Our “reasonable wait time”
standard, see United States v. Banks, 540 U. S. 31, 41
(2003), is necessarily vague. Banks (a drug case, like this
one) held that the proper measure was not how long it
would take the resident to reach the door, but how long it
would take to dispose of the suspected drugs—but that such
a time (15 to 20 seconds in that case) would necessarily be
extended when, for instance, the suspected contraband was
not easily concealed. Id., at 40–41. If our ex post evaluation
is subject to such calculations, it is unsurprising that, ex
ante, police officers about to encounter someone who may
try to harm them will be uncertain how long to wait.
Happily, these issues do not confront us here. From the
trial level onward, Michigan has conceded that the entry
was a knock-and-announce violation. The issue here is
remedy. Wilson specifically declined to decide whether the
exclusionary rule is appropriate for violation of the knock-
and-announce requirement. 514 U. S., at 937, n. 4. That
question is squarely before us now.
III

A

In Weeks v. United States, 232 U. S. 383 (1914), we
adopted the federal exclusionary rule for evidence that was
unlawfully seized from a home without a warrant in viola
tion of the Fourth Amendment. We began applying the
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same rule to the States, through the Fourteenth Amend
ment, in Mapp v. Ohio, 367 U. S. 643 (1961).
Suppression of evidence, however, has always been our
last resort, not our first impulse. The exclusionary rule
generates “substantial social costs,” United States v. Leon,
468 U. S. 897, 907 (1984), which sometimes include setting
the guilty free and the dangerous at large. We have there
fore been “cautio[us] against expanding” it, Colorado v.
Connelly, 479 U. S. 157, 166 (1986), and “have repeatedly
emphasized that the rule’s ‘costly toll’ upon truth-seeking
and law enforcement objectives presents a high obstacle
for those urging [its] application,” Pennsylvania Bd. of
Probation and Parole v. Scott, 524 U. S. 357, 364–365
(1998) (citation omitted). We have rejected “[i]ndiscrimi
nate application” of the rule, Leon, supra, at 908, and have
held it to be applicable only “where its remedial objectives
are thought most efficaciously served,” United States v.
Calandra, 414 U. S. 338, 348 (1974)—that is, “where its
deterrence benefits outweigh its ‘substantial social costs,’ ”
Scott, supra, at 363 (quoting Leon, supra, at 907).
We did not always speak so guardedly. Expansive dicta
in Mapp, for example, suggested wide scope for the exclu
sionary rule. See, e.g., 367 U. S., at 655 (“[A]ll evidence
obtained by searches and seizures in violation of the Con
stitution is, by that same authority, inadmissible in a
state court”). Whiteley v. Warden, Wyo. State Penitentiary,
401 U. S. 560, 568–569 (1971), was to the same effect. But
we have long since rejected that approach. As explained
in Arizona v. Evans, 514 U. S. 1, 13 (1995): “In Whiteley,
the Court treated identification of a Fourth Amendment
violation as synonymous with application of the exclusion
ary rule to evidence secured incident to that violation.
Subsequent case law has rejected this reflexive application
of the exclusionary rule.” (Citation omitted.) We had said
as much in Leon, a decade earlier, when we explained that
“[w]hether the exclusionary sanction is appropriately
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Opinion of the Court

imposed in a particular case, . . . is ‘an issue separate from
the question whether the Fourth Amendment rights of the
party seeking to invoke the rule were violated by police
conduct.’ ” 468 U. S., at 906 (quoting Illinois v. Gates, 462
U. S. 213, 223 (1983)).
In other words, exclusion may not be premised on the
mere fact that a constitutional violation was a “but-for”
cause of obtaining evidence. Our cases show that but-for
causality is only a necessary, not a sufficient, condition for
suppression. In this case, of course, the constitutional
violation of an illegal manner of entry was not a but-for
cause of obtaining the evidence. Whether that prelimi
nary misstep had occurred or not, the police would have
executed the warrant they had obtained, and would have
discovered the gun and drugs inside the house. But even
if the illegal entry here could be characterized as a but-for
cause of discovering what was inside, we have “never held
that evidence is ‘fruit of the poisonous tree’ simply because
‘it would not have come to light but for the illegal actions
of the police.’ ” Segura v. United States, 468 U. S. 796, 815
(1984). See also id., at 829 (STEVENS, J., dissenting) (“We
have not . . . mechanically applied the [exclusionary] rule to
every item of evidence that has a causal connection with
police misconduct”). Rather, but-for cause, or “causation in
the logical sense alone,” United States v. Ceccolini, 435
U. S. 268, 274 (1978), can be too attenuated to justify exclu
sion, id., at 274–275. Even in the early days of the exclu
sionary rule, we declined to
“hold that all evidence is ‘fruit of the poisonous tree’
simply because it would not have come to light but for
the illegal actions of the police. Rather, the more apt
question in such a case is ‘whether, granting estab
lishment of the primary illegality, the evidence to
which instant objection is made has been come at by
exploitation of that illegality or instead by means suf
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Opinion of the Court

ficiently distinguishable to be purged of the primary
taint.’ ” Wong Sun v. United States, 371 U. S. 471, 487–
488 (1963) (quoting J. Maguire, Evidence of Guilt 221
(1959) (emphasis added)).
Attenuation can occur, of course, when the causal con
nection is remote. See, e.g., Nardone v. United States, 308
U. S. 338, 341 (1939). Attenuation also occurs when, even
given a direct causal connection, the interest protected by
the constitutional guarantee that has been violated would
not be served by suppression of the evidence obtained.
“The penalties visited upon the Government, and in turn
upon the public, because its officers have violated the law
must bear some relation to the purposes which the law is
to serve.” Ceccolini, supra, at 279. Thus, in New York v.
Harris, 495 U. S. 14 (1990), where an illegal warrantless
arrest was made in Harris’ house, we held that
“suppressing [Harris’] statement taken outside the
house would not serve the purpose of the rule that
made Harris’ in-house arrest illegal. The warrant re
quirement for an arrest in the home is imposed to pro
tect the home, and anything incriminating the police
gathered from arresting Harris in his home, rather
than elsewhere, has been excluded, as it should have
been; the purpose of the rule has thereby been vindi
cated.” Id., at 20.
For this reason, cases excluding the fruits of unlawful
warrantless searches, see, e.g., Boyd v. United States, 116
U. S. 616 (1886); Weeks, 232 U. S. 383; Silverthorne Lumber
Co. v. United States, 251 U. S. 385 (1920); Mapp, supra, say
nothing about the appropriateness of exclusion to vindi
cate the interests protected by the knock-and-announce
requirement. Until a valid warrant has issued, citizens
are entitled to shield “their persons, houses, papers, and
effects,” U. S. Const., Amdt. 4, from the government’s
scrutiny. Exclusion of the evidence obtained by a war
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Opinion of the Court

rantless search vindicates that entitlement. The interests
protected by the knock-and-announce requirement are
quite different—and do not include the shielding of poten
tial evidence from the government’s eyes.
One of those interests is the protection of human life
and limb, because an unannounced entry may provoke
violence in supposed self-defense by the surprised resi
dent. See, e.g., McDonald v. United States, 335 U. S. 451,
460–461 (1948) (Jackson, J., concurring). See also Sabbath,
391 U. S., at 589; Miller, 357 U. S., at 313, n. 12. Another
interest is the protection of property. Breaking a house (as
the old cases typically put it) absent an announcement
would penalize someone who “ ‘did not know of the process,
of which, if he had notice, it is to be presumed that he
would obey it . . . .’ ” Wilson, 514 U. S., at 931–932 (quot
ing Semayne’s Case, 5 Co. Rep. 91a, 91b, 77 Eng. Rep. 194,
195–196 (K. B. 1603)). The knock-and-announce rule gives
individuals “the opportunity to comply with the law and to
avoid the destruction of property occasioned by a forcible
entry.” Richards, 520 U. S., at 393, n. 5. See also Banks,
540 U. S., at 41. And thirdly, the knock-and-announce rule
protects those elements of privacy and dignity that can be
destroyed by a sudden entrance. It gives residents the
“opportunity to prepare themselves for” the entry of the
police. Richards, 520 U. S., at 393, n. 5. “The brief inter
lude between announcement and entry with a warrant
may be the opportunity that an individual has to pull on
clothes or get out of bed.” Ibid. In other words, it assures
the opportunity to collect oneself before answering the
door.
What the knock-and-announce rule has never protected,
however, is one’s interest in preventing the government
from seeing or taking evidence described in a warrant.
Since the interests that were violated in this case have
nothing to do with the seizure of the evidence, the exclu
sionary rule is inapplicable.
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Opinion of the Court

B
Quite apart from the requirement of unattenuated
causation, the exclusionary rule has never been applied
except “where its deterrence benefits outweigh its ‘sub
stantial social costs,’ ” Scott, 524 U. S., at 363 (quoting
Leon, 468 U. S., at 907). The costs here are considerable.
In addition to the grave adverse consequence that exclu
sion of relevant incriminating evidence always entails
(viz., the risk of releasing dangerous criminals into soci
ety), imposing that massive remedy for a knock-and
announce violation would generate a constant flood of
alleged failures to observe the rule, and claims that any
asserted Richards justification for a no-knock entry, see
520 U. S., at 394, had inadequate support. Cf. United
States v. Singleton, 441 F. 3d 290, 293–294 (CA4 2006).
The cost of entering this lottery would be small, but the
jackpot enormous: suppression of all evidence, amounting
in many cases to a get-out-of-jail-free card. Courts would
experience as never before the reality that “[t]he exclu
sionary rule frequently requires extensive litigation to
determine whether particular evidence must be excluded.”
Scott, supra, at 366. Unlike the warrant or Miranda
requirements, compliance with which is readily deter
mined (either there was or was not a warrant; either the
Miranda warning was given, or it was not), what consti
tuted a “reasonable wait time” in a particular case, Banks,
supra, at 41 (or, for that matter, how many seconds the
police in fact waited), or whether there was “reasonable
suspicion” of the sort that would invoke the Richards
exceptions, is difficult for the trial court to determine and
even more difficult for an appellate court to review.
Another consequence of the incongruent remedy Hudson
proposes would be police officers’ refraining from timely
entry after knocking and announcing. As we have ob
served, see supra, at 3, the amount of time they must wait
is necessarily uncertain. If the consequences of running
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Opinion of the Court

afoul of the rule were so massive, officers would be in
clined to wait longer than the law requires—producing
preventable violence against officers in some cases, and
the destruction of evidence in many others. See Gates, 462
U. S., at 258. We deemed these consequences severe
enough to produce our unanimous agreement that a mere
“reasonable suspicion” that knocking and announcing
“under the particular circumstances, would be dangerous
or futile, or that it would inhibit the effective investigation
of the crime,” will cause the requirement to yield. Rich
ards, supra, at 394.
Next to these “substantial social costs” we must consider
the deterrence benefits, existence of which is a necessary
condition for exclusion. (It is not, of course, a sufficient
condition: “[I]t does not follow that the Fourth Amend
ment requires adoption of every proposal that might deter
police misconduct.” Calandra, 414 U. S., at 350; see also
Leon, supra, at 910.) To begin with, the value of deter
rence depends upon the strength of the incentive to com
mit the forbidden act. Viewed from this perspective,
deterrence of knock-and-announce violations is not worth
a lot. Violation of the warrant requirement sometimes
produces incriminating evidence that could not otherwise
be obtained. But ignoring knock-and-announce can realis
tically be expected to achieve absolutely nothing except
the prevention of destruction of evidence and the avoid
ance of life-threatening resistance by occupants of the
premises—dangers which, if there is even “reasonable
suspicion” of their existence, suspend the knock-and
announce requirement anyway. Massive deterrence is
hardly required.
It seems to us not even true, as Hudson contends, that
without suppression there will be no deterrence of knock-
and-announce violations at all. Of course even if this
assertion were accurate, it would not necessarily justify
suppression. Assuming (as the assertion must) that civil
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Opinion of the Court

suit is not an effective deterrent, one can think of many
forms of police misconduct that are similarly “undeterred.”
When, for example, a confessed suspect in the killing of a
police officer, arrested (along with incriminating evidence)
in a lawful warranted search, is subjected to physical
abuse at the station house, would it seriously be suggested
that the evidence must be excluded, since that is the only
“effective deterrent”? And what, other than civil suit, is
the “effective deterrent” of police violation of an already-
confessed suspect’s Sixth Amendment rights by denying
him prompt access to counsel? Many would regard these
violated rights as more significant than the right not to be
intruded upon in one’s nightclothes—and yet nothing but
“ineffective” civil suit is available as a deterrent. And the
police incentive for those violations is arguably greater
than the incentive for disregarding the knock-and
announce rule.
We cannot assume that exclusion in this context is
necessary deterrence simply because we found that it was
necessary deterrence in different contexts and long ago.
That would be forcing the public today to pay for the sins
and inadequacies of a legal regime that existed almost half
a century ago. Dollree Mapp could not turn to 42 U. S. C.
§1983 for meaningful relief; Monroe v. Pape, 365 U. S. 167
(1961), which began the slow but steady expansion of that
remedy, was decided the same Term as Mapp. It would be
another 17 years before the §1983 remedy was extended to
reach the deep pocket of municipalities, Monell v. New
York City Dept. of Social Servs., 436 U. S. 658 (1978).
Citizens whose Fourth Amendment rights were violated
by federal officers could not bring suit until 10 years after
Mapp, with this Court’s decision in Bivens v. Six Unknown
Fed. Narcotics Agents, 403 U. S. 388 (1971).
Hudson complains that “it would be very hard to find a
lawyer to take a case such as this,” Tr. of Oral Arg. 7, but
42 U. S. C. §1988(b) answers this objection. Since some
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Opinion of the Court

civil-rights violations would yield damages too small to
justify the expense of litigation, Congress has authorized
attorney’s fees for civil-rights plaintiffs. This remedy was
unavailable in the heydays of our exclusionary-rule juris
prudence, because it is tied to the availability of a cause of
action. For years after Mapp, “very few lawyers would
even consider representation of persons who had civil
rights claims against the police,” but now “much has
changed. Citizens and lawyers are much more willing to
seek relief in the courts for police misconduct.” M. Avery,
D. Rudovsky, & K. Blum, Police Misconduct: Law and
Litigation, p. v (3d ed. 2005); see generally N. Aron, Lib
erty and Justice for All: Public Interest Law in the 1980s
and Beyond (1989) (describing the growth of public-
interest law). The number of public-interest law firms and
lawyers who specialize in civil-rights grievances has
greatly expanded.
Hudson points out that few published decisions to date
announce huge awards for knock-and-announce violations.
But this is an unhelpful statistic. Even if we thought that
only large damages would deter police misconduct (and
that police somehow are deterred by “damages” but indif
ferent to the prospect of large §1988 attorney’s fees), we do
not know how many claims have been settled, or indeed
how many violations have occurred that produced any
thing more than nominal injury. It is clear, at least, that
the lower courts are allowing colorable knock-and
announce suits to go forward, unimpeded by assertions of
qualified immunity. See, e.g., Green v. Butler, 420 F. 3d
689, 700–701 (CA7 2005) (denying qualified immunity in a
knock-and-announce civil suit); Holland ex rel. Overdorff
v. Harrington, 268 F. 3d 1179, 1193–1196 (CA10 2001)
(same); Mena v. Simi Valley, 226 F. 3d 1031, 1041–1042
(CA9 2000) (same); Gould v. Davis, 165 F. 3d 265, 270–271
(CA4 1998) (same). As far as we know, civil liability is an
effective deterrent here, as we have assumed it is in other
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Opinion of the Court

contexts. See, e.g., Correctional Services Corp. v. Malesko,
534 U. S. 61, 70 (2001) (“[T]he threat of litigation and liabil
ity will adequately deter federal officers for Bivens purposes
no matter that they may enjoy qualified immunity” (as
violators of knock-and-announce do not)); see also Nix v.
Williams, 467 U. S. 431, 446 (1984).
Another development over the past half-century that
deters civil-rights violations is the increasing professional
ism of police forces, including a new emphasis on internal
police discipline. Even as long ago as 1980 we felt it
proper to “assume” that unlawful police behavior would
“be dealt with appropriately” by the authorities, United
States v. Payner, 447 U. S. 727, 733–734, n. 5 (1980), but
we now have increasing evidence that police forces across
the United States take the constitutional rights of citizens
seriously. There have been “wide-ranging reforms in the
education, training, and supervision of police officers.” S.
Walker, Taming the System: The Control of Discretion in
Criminal Justice 1950–1990, p. 51 (1993). Numerous
sources are now available to teach officers and their su
pervisors what is required of them under this Court’s
cases, how to respect constitutional guarantees in various
situations, and how to craft an effective regime for inter
nal discipline. See, e.g., D. Waksman & D. Goodman, The
Search and Seizure Handbook (2d ed. 2006); A. Stone & S.
DeLuca, Police Administration: An Introduction (2d ed.
1994); E. Thibault, L. Lynch, & R. McBridge, Proactive
Police Management (4th ed. 1998). Failure to teach and
enforce constitutional requirements exposes municipalities
to financial liability. See Canton v. Harris, 489 U. S. 378,
388 (1989). Moreover, modern police forces are staffed
with professionals; it is not credible to assert that internal
discipline, which can limit successful careers, will not have
a deterrent effect. There is also evidence that the increas
ing use of various forms of citizen review can enhance
police accountability.
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Opinion of SCALIA, J.

In sum, the social costs of applying the exclusionary rule
to knock-and-announce violations are considerable; the
incentive to such violations is minimal to begin with, and
the extant deterrences against them are substantial—
incomparably greater than the factors deterring
warrantless entries when Mapp was decided. Resort to
the massive remedy of suppressing evidence of guilt is
unjustified.
IV
A trio of cases—Segura v. United States, 468 U. S. 796
(1984); New York v. Harris, 495 U. S. 14 (1990); and United
States v. Ramirez, 523 U. S. 65 (1998)—confirms our con
clusion that suppression is unwarranted in this case.
Like today’s case, Segura involved a concededly illegal
entry. Police conducting a drug crime investigation waited
for Segura outside an apartment building; when he ar
rived, he denied living there. The police arrested him and
brought him to the apartment where they suspected illegal
activity. An officer knocked. When someone inside
opened the door, the police entered, taking Segura with
them. They had neither a warrant nor consent to enter,
and they did not announce themselves as police—an entry
as illegal as can be. Officers then stayed in the apartment
for 19 hours awaiting a search warrant. 468 U. S., at 800–
801; id., at 818–819 (STEVENS, J., dissenting). Once
alerted that the search warrant had been obtained, the
police—still inside, having secured the premises so that no
evidence could be removed—conducted a search. Id., at
801. We refused to exclude the resulting evidence. We
recognized that only the evidence gained from the particu
lar violation could be excluded, see id., at 799, 804–805,
and therefore distinguished the effects of the illegal entry
from the effects of the legal search: “None of the informa
tion on which the warrant was secured was derived from
or related in any way to the initial entry into petitioners’
14 HUDSON v. MICHIGAN

Opinion of SCALIA, J.

apartment . . . .” Id., at 814. It was therefore “beyond
dispute that the information possessed by the agents
before they entered the apartment constituted an inde
pendent source for the discovery and seizure of the evi
dence now challenged.” Ibid.
If the search in Segura could be “wholly unrelated to the
prior entry,” ibid., when the only entry was warrantless, it
would be bizarre to treat more harshly the actions in this
case, where the only entry was with a warrant. If the
probable cause backing a warrant that was issued later in
time could be an “independent source” for a search that
proceeded after the officers illegally entered and waited, a
search warrant obtained before going in must have at least
this much effect.1
In the second case, Harris, the police violated the defen
dant’s Fourth Amendment rights by arresting him at
home without a warrant, contrary to Payton v. New York,
445 U. S. 573 (1980). Once taken to the station house, he
gave an incriminating statement. See 495 U. S., at 15–16.
We refused to exclude it. Like the illegal entry which led
——————
1 JUSTICE BREYER’s insistence that the warrant in Segura was “ob
tained independently without use of any information found during the
illegal entry,” post, at 14 (dissenting opinion), entirely fails to distin
guish it from the warrant in the present case. Similarly inapposite is
his appeal to Justice Frankfurter’s statement in Wolf v. Colorado, 338
U. S. 25, 28 (1949), that the “knock at the door, . . . as a prelude to a
search, without authority of law . . . [is] inconsistent with the concep
tion of human rights enshrined in [our] history,” see post, at 17. “How
much the more offensive,” JUSTICE BREYER asserts, “when the search
takes place without any knock at all,” ibid. But a no-knock entry
“without authority of law” (i.e., without a search warrant) describes not
this case, but Segura—where the evidence was admitted anyway.
JUSTICE BREYER’s assertion that Segura, unlike our decision in the
present case, had no effect on deterrence, see post, at 23, does not
comport with the views of the Segura dissent. See, e.g., 468 U. S., at
817 (STEVENS, J., dissenting) (“The Court’s disposition, I fear, will
provide government agents with an affirmative incentive to engage in
unconstitutional violations of the privacy of the home”).
 Cite as: 547 U. S. ____ (2006) 15

Opinion of SCALIA, J.

to discovery of the evidence in today’s case, the illegal
arrest in Harris began a process that culminated in acqui
sition of the evidence sought to be excluded. While Har
ris’s statement was “the product of an arrest and being in
custody,” it “was not the fruit of the fact that the arrest
was made in the house rather than someplace else.” Id.,
at 20. Likewise here: While acquisition of the gun and
drugs was the product of a search pursuant to warrant, it
was not the fruit of the fact that the entry was not pre
ceded by knock and announce.2
United States v. Ramirez, supra, involved a claim that
police entry violated the Fourth Amendment because it was
effected by breaking a window. We ultimately concluded
that the property destruction was, under all the circum
stances, reasonable, but in the course of our discussion we
unanimously said the following: “[D]estruction of property
in the course of a search may violate the Fourth Amend
ment, even though the entry itself is lawful and the fruits of
the search are not subject to suppression.” Id., at 71. Had
the breaking of the window been unreasonable, the Court
said, it would have been necessary to determine whether
there had been a “sufficient causal relationship between the
breaking of the window and the discovery of the guns to
warrant suppression of the evidence.” Id., at 72, n. 3. What
clearer expression could there be of the proposition that an

——————
2 Harris undermines two key points of the dissent. First, the claim

that “whether the interests underlying the knock-and-announce rule
are implicated in any given case is, in a sense, beside the point,” post, at
18. This is flatly refuted by Harris’s plain statement that the reason
for a rule must govern the sanctions for the rule’s violation. 495 U. S.,
at 17, 20; see also supra, at 6. Second, the dissent’s attempt to turn
Harris into a vindication of the sanctity of the home, see post, at 24.
The whole point of the case was that a confession that police obtained
by illegally removing a man from the sanctity of his home was admissi
ble against him.
16 HUDSON v. MICHIGAN

Opinion of SCALIA, J.

impermissible manner of entry does not necessarily trigger
the exclusionary rule?
* * *
For the foregoing reasons we affirm the judgment of the
Michigan Court of Appeals.
It is so ordered.
 Cite as: 547 U. S. ____ (2006) 1

Opinion of KENNEDY, J.

SUPREME COURT OF THE UNITED STATES
_________________

No. 04–1360
_________________

BOOKER T. HUDSON, JR., PETITIONER v. MICHIGAN
ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF

MICHIGAN

[June 15, 2006]

JUSTICE KENNEDY, concurring in part and concurring in
the judgment.
Two points should be underscored with respect to to
day’s decision. First, the knock-and-announce require
ment protects rights and expectations linked to ancient
principles in our constitutional order. See Wilson v. Ar
kansas, 514 U. S. 927, 934 (1995). The Court’s decision
should not be interpreted as suggesting that violations of
the requirement are trivial or beyond the law’s concern.
Second, the continued operation of the exclusionary rule,
as settled and defined by our precedents, is not in doubt.
Today’s decision determines only that in the specific con
text of the knock-and-announce requirement, a violation is
not sufficiently related to the later discovery of evidence to
justify suppression.
As to the basic right in question, privacy and security in
the home are central to the Fourth Amendment’s guaran
tees as explained in our decisions and as understood since
the beginnings of the Republic. This common understand
ing ensures respect for the law and allegiance to our insti
tutions, and it is an instrument for transmitting our Con
stitution to later generations undiminished in meaning
and force. It bears repeating that it is a serious matter if
law enforcement officers violate the sanctity of the home
by ignoring the requisites of lawful entry. Security must
not be subject to erosion by indifference or contempt.
2 HUDSON v. MICHIGAN

Opinion of KENNEDY, J.

Our system, as the Court explains, has developed proce
dures for training police officers and imposing discipline
for failures to act competently and lawfully. If those
measures prove ineffective, they can be fortified with more
detailed regulations or legislation. Supplementing these
safeguards are civil remedies, such as those available
under 42 U. S. C. §1983, that provide restitution for dis
crete harms. These remedies apply to all violations, in
cluding, of course, exceptional cases in which unan
nounced entries cause severe fright and humiliation.
Suppression is another matter. Under our precedents
the causal link between a violation of the knock-and
announce requirement and a later search is too attenuated
to allow suppression. Cf. United States v. Ramirez, 523
U. S. 65, 72, n. 3 (1998) (application of the exclusionary
rule depends on the existence of a “sufficient causal rela
tionship” between the unlawful conduct and the discovery
of evidence). When, for example, a violation results from
want of a 20-second pause but an ensuing, lawful search
lasting five hours discloses evidence of criminality, the
failure to wait at the door cannot properly be described as
having caused the discovery of evidence.
Today’s decision does not address any demonstrated
pattern of knock-and-announce violations. If a widespread
pattern of violations were shown, and particularly if those
violations were committed against persons who lacked the
means or voice to mount an effective protest, there would
be reason for grave concern. Even then, however, the
Court would have to acknowledge that extending the
remedy of exclusion to all the evidence seized following a
knock-and-announce violation would mean revising the
requirement of causation that limits our discretion in
applying the exclusionary rule. That type of extension
also would have significant practical implications, adding
to the list of issues requiring resolution at the criminal
trial questions such as whether police officers entered a
 Cite as: 547 U. S. ____ (2006) 3

Opinion of KENNEDY, J.

home after waiting 10 seconds or 20.
In this case the relevant evidence was discovered not
because of a failure to knock-and-announce, but because of
a subsequent search pursuant to a lawful warrant. The
Court in my view is correct to hold that suppression was
not required. While I am not convinced that Segura v.
United States, 468 U. S. 796 (1984), and New York v. Harris,
495 U. S. 14 (1990), have as much relevance here as
JUSTICE SCALIA appears to conclude, the Court’s holding is
fully supported by Parts I through III of its opinion. I ac
cordingly join those Parts and concur in the judgment.
 Cite as: 547 U. S. ____ (2006) 1

BREYER, J., dissenting

SUPREME COURT OF THE UNITED STATES
_________________

No. 04–1360
_________________

BOOKER T. HUDSON, JR., PETITIONER v. MICHIGAN
ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF

MICHIGAN

[June 15, 2006]

JUSTICE BREYER, with whom JUSTICE STEVENS, JUSTICE
SOUTER, and JUSTICE GINSBURG join, dissenting.
In Wilson v. Arkansas, 514 U. S. 927 (1995), a unani
mous Court held that the Fourth Amendment normally
requires law enforcement officers to knock and announce
their presence before entering a dwelling. Today’s opinion
holds that evidence seized from a home following a viola
tion of this requirement need not be suppressed
As a result, the Court destroys the strongest legal incen
tive to comply with the Constitution’s knock-and-announce
requirement. And the Court does so without significant
support in precedent. At least I can find no such support
in the many Fourth Amendment cases the Court has
decided in the near century since it first set forth the
exclusionary principle in Weeks v. United States, 232 U. S.
383 (1914). See Appendix, infra.
Today’s opinion is thus doubly troubling. It represents a
significant departure from the Court’s precedents. And it
weakens, perhaps destroys, much of the practical value of
the Constitution’s knock-and-announce protection.
I
This Court has set forth the legal principles that ought
to have determined the outcome of this case in two sets of
basic Fourth Amendment cases. I shall begin by describ
2 HUDSON v. MICHIGAN

BREYER, J., dissenting

ing that underlying case law.
A
The first set of cases describes the constitutional knock-
and-announce requirement, a requirement that this Court
initially set forth only 11 years ago in Wilson v. Arkansas,
supra. Cf. Sabbath v. United States, 391 U. S. 585 (1968)
(suppressing evidence seized in violation of federal statu
tory knock-and-announce requirement); Miller v. United
States, 357 U. S. 301 (1958) (same). In Wilson, tracing the
lineage of the knock-and-announce rule back to the 13th
century, 514 U. S., at 932, we wrote that
“[a]n examination of the common law of search and
seizure leaves no doubt that the reasonableness of a
search of a dwelling may depend in part on whether
law enforcement officers announced their presence
and authority prior to entering.” Id., at 931.
We noted that this “basic principle” was agreed upon by
“[s]everal prominent founding-era commentators,” id., at
932, and “was woven quickly into the fabric of early
American law” via state constitutions and statutes, id., at
933. We further concluded that there was
“little doubt that the Framers of the Fourth Amend
ment thought that the method of an officer’s entry
into a dwelling was among the factors to be considered
in assessing the reasonableness of a search or sei
zure.” Id., at 934.
And we held that the “common-law ‘knock and an
nounce’ principle forms a part of the reasonableness in
quiry under the Fourth Amendment.” Id., at 929. Thus,
“a search or seizure of a dwelling might be constitutionally
defective if police officers enter without prior announce
ment.” Id., at 936; see United States v. Banks, 540 U. S.
31, 36 (2003); United States v. Ramirez, 523 U. S. 65, 70
(1998); Richards v. Wisconsin, 520 U. S. 385, 387 (1997).
 Cite as: 547 U. S. ____ (2006) 3

BREYER, J., dissenting

B
The second set of cases sets forth certain well-
established principles that are relevant here. They in
clude:
Boyd v. United States, 116 U. S. 616 (1886). In this semi
nal Fourth Amendment case, decided 120 years ago, the
Court wrote, in frequently quoted language, that the
Fourth Amendment’s prohibitions apply
“to all invasions on the part of the government and its
employés of the sanctity of a man’s home and the pri
vacies of life. It is not the breaking of his doors, and
the rummaging of his drawers, that constitutes the
essence of the offence; but it is the invasion of his in
defeasible right of personal security, personal liberty
and private property.” Id., at 630.
Weeks, supra. This case, decided 28 years after Boyd,
originated the exclusionary rule. The Court held that the
Federal Government could not retain evidence seized
unconstitutionally and use that evidence in a federal
criminal trial. The Court pointed out that “[i]f letters and
private documents” could be unlawfully seized from a
home “and used in evidence against a citizen accused of an
offense, the protection of the Fourth Amendment declaring
his right to be secure against such searches and seizures is
of no value, and . . . might as well be stricken from the
Constitution.” 232 U. S., at 393.
Silverthorne Lumber Co. v. United States, 251 U. S. 385
(1920). This case created an exception to (or a qualifica
tion of) Weeks’ exclusionary rule. The Court held that the
Government could not use information obtained during an
illegal search to subpoena documents that they illegally
viewed during that search. Writing for the Court, Justice
Holmes noted that the exclusionary rule “does not mean
that the facts [unlawfully] obtained become sacred and
inaccessible. If knowledge of them is gained from an
4 HUDSON v. MICHIGAN

BREYER, J., dissenting

independent source they may be proved like any
others . . . .” 251 U. S., at 392. Silverthorne thus stands
for the proposition that the exclusionary rule does not
apply if the evidence in question (or the “fruits” of that
evidence) was obtained through a process unconnected
with, and untainted by, the illegal search. Cf. Nix v. Wil
liams, 467 U. S. 431, 444 (1984) (describing related “inevi
table discovery” exception).
Wolf v. Colorado, 338 U. S. 25 (1949), and Mapp v. Ohio,
367 U. S. 643 (1961). Both of these cases considered
whether Weeks’ exclusionary rule applies to the States. In
Wolf, the Court held that it did not. It said that “[t]he
security of one’s privacy against arbitrary intrusion by the
police . . . is . . . implicit in ‘the concept of ordered liberty’
and as such enforceable against the States through the
Due Process Clause.” 338 U. S., at 27–28. But the Court
held that the exclusionary rule is not enforceable against
the States as “an essential ingredient of the right.” Id., at
29. In Mapp, the Court overruled Wolf. Experience, it
said, showed that alternative methods of enforcing the
Fourth Amendment’s requirements had failed. See 367
U. S., at 651–653; see, e.g., People v. Cahan, 44 Cal. 2d
434, 447, 282 P. 2d 905, 913 (1955) (Traynor, C. J.) (“Ex
perience [in California] has demonstrated, however, that
neither administrative, criminal nor civil remedies are
effective in suppressing lawless searches and seizures”).
The Court consequently held that “all evidence obtained
by searches and seizures in violation of the Constitution
is, by that same authority, inadmissible in a state court.”
Mapp, 367 U. S., at 655. “To hold otherwise,” the Court
added, would be “to grant the right but in reality to with
hold its privilege and enjoyment.” Id., at 656.
II
Reading our knock-and-announce cases, Part I–A, su
pra, in light of this foundational Fourth Amendment case
 Cite as: 547 U. S. ____ (2006) 5

BREYER, J., dissenting

law, Part I–B, supra, it is clear that the exclusionary rule
should apply. For one thing, elementary logic leads to
that conclusion. We have held that a court must “con-
side[r]” whether officers complied with the knock-and
announce requirement “in assessing the reasonableness of
a search or seizure.” Wilson, 514 U. S., at 934 (emphasis
added); see Banks, 540 U. S., at 36. The Fourth Amend
ment insists that an unreasonable search or seizure is,
constitutionally speaking, an illegal search or seizure.
And ever since Weeks (in respect to federal prosecutions)
and Mapp (in respect to state prosecutions), “the use of
evidence secured through an illegal search and seizure” is
“barred” in criminal trials. Wolf, supra, at 28 (citing
Weeks); see Mapp, supra, at 655.
For another thing, the driving legal purpose underlying
the exclusionary rule, namely, the deterrence of unlawful
government behavior, argues strongly for suppression.
See Elkins v. United States, 364 U. S. 206, 217 (1960) (pur
pose of the exclusionary rule is “to deter—to compel re
spect for the constitutional guaranty . . . by removing the
incentive to disregard it”). In Weeks, Silverthorne, and
Mapp, the Court based its holdings requiring suppression
of unlawfully obtained evidence upon the recognition that
admission of that evidence would seriously undermine the
Fourth Amendment’s promise. All three cases recognized
that failure to apply the exclusionary rule would make
that promise a hollow one, see Mapp, supra, at 657, reduc
ing it to “a form of words,” Silverthorne, supra, at 392, “of
no value” to those whom it seeks to protect, Weeks, supra,
at 393. Indeed, this Court in Mapp held that the exclu
sionary rule applies to the States in large part due to its
belief that alternative state mechanisms for enforcing the
Fourth Amendment’s guarantees had proved “worthless
and futile.” 367 U. S., at 652.
Why is application of the exclusionary rule any the less
necessary here? Without such a rule, as in Mapp, police
6 HUDSON v. MICHIGAN

BREYER, J., dissenting

know that they can ignore the Constitution’s requirements
without risking suppression of evidence discovered after
an unreasonable entry. As in Mapp, some government
officers will find it easier, or believe it less risky, to pro
ceed with what they consider a necessary search immedi
ately and without the requisite constitutional (say, war
rant or knock-and-announce) compliance. Cf. Mericli, The
Apprehension of Peril Exception to the Knock and An
nounce Rule—Part I, 16 Search and Seizure L. Rep. 129,
130 (1989) (hereinafter Mericili) (noting that some “[d]rug
enforcement authorities believe that safety for the police
lies in a swift, surprising entry with overwhelming force—
not in announcing their official authority”).
Of course, the State or the Federal Government may
provide alternative remedies for knock-and-announce
violations. But that circumstance was true of Mapp as
well. What reason is there to believe that those remedies
(such as private damages actions under 42 U. S. C. §1983),
which the Court found inadequate in Mapp, can ade
quately deter unconstitutional police behavior here? See
Kamisar, In Defense of the Search and Seizure Exclusion
ary Rule, 26 Harv. J. L. & Pub. Pol’y 119, 126–129 (2003)
(arguing that “five decades of post-Weeks ‘freedom’ from
the inhibiting effect of the federal exclusionary rule failed
to produce any meaningful alternative to the exclusionary
rule in any jurisdiction” and that there is no evidence that
“times have changed” post-Mapp).
The cases reporting knock-and-announce violations are
legion. See, e.g., 34 Geo. L. J. Ann. Rev. Crim. Proc. 31–35
(2005) (collecting court of appeals cases); Annot., 85
A. L. R. 5th 1 (2001) (collecting state-court cases); Brief for
Petitioner 16–17 (collecting federal and state cases).
Indeed, these cases of reported violations seem sufficiently
frequent and serious as to indicate “a widespread pattern.”
Ante, at 2 (KENNEDY, J., concurring in part and concurring
in judgment). Yet the majority, like Michigan and the
 Cite as: 547 U. S. ____ (2006) 7

BREYER, J., dissenting

United States, has failed to cite a single reported case in
which a plaintiff has collected more than nominal dam
ages solely as a result of a knock-and-announce violation.
Even Michigan concedes that, “in cases like the present
one . . . , damages may be virtually non-existent.” Brief for
Respondent 35, n. 66; And Michigan’s amici further con
cede that civil immunities prevent tort law from being an
effective substitute for the exclusionary rule at this time.
Brief for Criminal Justice Legal Foundation 10; see also
Hope v. Pelzer, 536 U. S. 730, 739 (2002) (difficulties of
overcoming qualified immunity defenses).
As Justice Stewart, the author of a number of signifi
cant Fourth Amendment opinions, explained, the deter
rent effect of damage actions “can hardly be said to be
great,” as such actions are “expensive, time-consuming,
not readily available, and rarely successful.” Stewart, The
Road to Mapp v. Ohio and Beyond: The Origins, Develop
ment and Future of the Exclusionary Rule in Search-and-
Seizure Cases, 83 Colum. L. Rev. 1365, 1388 (1983). The
upshot is that the need for deterrence—the critical factor
driving this Court’s Fourth Amendment cases for close to a
century—argues with at least comparable strength for
evidentiary exclusion here.
To argue, as the majority does, that new remedies, such
as 42 U. S. C. §1983 actions or better trained police, make
suppression unnecessary is to argue that Wolf, not Mapp,
is now the law. (The Court recently rejected a similar
argument in Dickerson v. United States, 530 U. S. 428, 441–
442 (2000).) To argue that there may be few civil suits
because violations may produce nothing “more than nomi
nal injury” is to confirm, not to deny, the inability of civil
suits to deter violations. See ante, at 11. And to argue
without evidence (and despite myriad reported cases of
violations, no reported case of civil damages, and Michi
gan’s concession of their nonexistence) that civil suits may
provide deterrence because claims may “have been settled”
8 HUDSON v. MICHIGAN

BREYER, J., dissenting

is, perhaps, to search in desperation for an argument. See
ibid. Rather, the majority, as it candidly admits, has
simply “assumed” that, “[a]s far as [it] know[s], civil liabil
ity is an effective deterrent,” ibid., a support-free assump
tion that Mapp and subsequent cases make clear does not
embody the Court’s normal approach to difficult questions
of Fourth Amendment law.
It is not surprising, then, that after looking at virtually
every pertinent Supreme Court case decided since Weeks, I
can find no precedent that might offer the majority sup
port for its contrary conclusion. The Court has, of course,
recognized that not every Fourth Amendment violation
necessarily triggers the exclusionary rule. Ante, at 4–5; cf.
Illinois v. Gates, 462 U. S. 213, 223 (1983) (application of
the exclusionary rule is a separate question from whether
the Fourth Amendment has been violated). But the class
of Fourth Amendment violations that do not result in
suppression of the evidence seized, however, is limited.
The Court has declined to apply the exclusionary rule
only:
(1) where there is a specific reason to believe that ap
plication of the rule would “not result in appreciable
deterrence,” United States v. Janis, 428 U. S. 433, 454
(1976); see, e.g., United States v. Leon, 468 U. S. 897,
919–920 (1984) (exception where searching officer exe
cutes defective search warrant in “good faith”); Ari
zona v. Evans, 514 U. S. 1, 14 (1995) (exception for
clerical errors by court employees); Walder v. United
States, 347 U. S. 62 (1954) (exception for impeach
ment purposes), or
(2) where admissibility in proceedings other than
criminal trials was at issue, see, e.g., Pennsylvania
Bd. of Probation and Parole v. Scott, 524 U. S. 357,
364 (1998) (exception for parole revocation proceed
ings); INS v. Lopez-Mendoza, 468 U. S. 1032, 1050
 Cite as: 547 U. S. ____ (2006) 9

BREYER, J., dissenting

(1984) (plurality opinion) (exception for deportation
proceedings); Janis, supra, at 458 (exception for civil
tax proceedings); United States v. Calandra, 414 U. S.
338, 348–350 (1974) (exception for grand jury proceed
ings); Stone v. Powell, 428 U. S. 465, 493–494 (1976)
(exception for federal habeas proceedings).
Neither of these two exceptions applies here. The sec
ond does not apply because this case is an ordinary crimi
nal trial. The first does not apply because (1) officers who
violate the rule are not acting “as a reasonable officer
would and should act in similar circumstances,” Leon,
supra, at 920, (2) this case does not involve government
employees other than police, Evans, supra, and (3), most
importantly, the key rationale for any exception, “lack of
deterrence,” is missing, see Pennsylvania Bd. of Probation,
supra, at 364 (noting that the rationale for not applying
the rule in noncriminal cases has been that the deterrence
achieved by having the rule apply in those contexts is
“minimal” because “application of the rule in the criminal
trial context already provides significant deterrence of
unconstitutional searches”); Michigan v. Tucker, 417 U. S.
433, 447 (1974) (noting that deterrence rationale would not
be served if rule applied to police officers acting in good
faith, as the “deterrent purpose of the exclusionary rule
necessarily assumes that the police have engaged in willful,
or at the very least negligent, conduct”). That critical latter
rationale, which underlies every exception, does not apply
here, as there is no reason to think that, in the case of
knock-and-announce violations by the police, “the exclu
sion of evidence at trial would not sufficiently deter future
errors,” Evans, supra, at 14, or “ ‘further the ends of the
exclusionary rule in any appreciable way,’ ” Leon, supra, at
919–920.
I am aware of no other basis for an exception. The
Court has decided more than 300 Fourth Amendment
10 HUDSON v. MICHIGAN

BREYER, J., dissenting

cases since Weeks. The Court has found constitutional
violations in nearly a third of them. See W. Greenhalgh,
The Fourth Amendment Handbook: A Chronological Sur
vey of Supreme Court Decisions 27–130 (2d ed. 2003)
(collecting and summarizing 332 post-Weeks cases decided
between 1914 and 2002). The nature of the constitutional
violation varies. In most instances officers lacked a war
rant; in others, officers possessed a warrant based on false
affidavits; in still others, the officers executed the search
in an unconstitutional manner. But in every case involv
ing evidence seized during an illegal search of a home
(federally since Weeks, nationally since Mapp), the Court,
with the exceptions mentioned, has either explicitly or
implicitly upheld (or required) the suppression of the
evidence at trial. See Appendix, infra. In not one of those
cases did the Court “questio[n], in the absence of a more
efficacious sanction, the continued application of the [ex
clusionary] rule to suppress evidence from the State’s
case” in a criminal trial. Franks v. Delaware, 438 U. S.
154, 171 (1978).
I can find nothing persuasive in the majority’s opinion
that could justify its refusal to apply the rule. It certain-
ly is not a justification for an exception here (as the major
ity finds) to find odd instances in other areas of law that
do not automatically demand suppression. Ante, at 10
(suspect confesses, police beat him up afterwards; sus-
pect confesses, then police apparently arrest him, take
him to station, and refuse to tell him of his right to coun
sel). Nor can it justify an exception to say that some
police may knock at the door anyway (to avoid being
mistaken for a burglar), for other police (believing
quick entry is the most secure, effective entry) will not
voluntarily do so. Cf. Mericli 130 (describing Special
Weapons and Tactics (SWAT) team practices); R.
Balko, No SWAT (Apr. 6, 2006), available at
http://www.cato.org/pub_display.php?pub_id=6344 (all In
 Cite as: 547 U. S. ____ (2006) 11

BREYER, J., dissenting

ternet materials as visited June 7, 2006, and available in
Clerk of Court’s case file).
Neither can the majority justify its failure to respect the
need for deterrence, as set forth consistently in the Court’s
prior case law, through its claim of “substantial social
costs”—at least if it means that those “social costs” are
somehow special here. The only costs it mentions are
those that typically accompany any use of the Fourth
Amendment’s exclusionary principle: (1) that where the
constable blunders, a guilty defendant may be set free
(consider Mapp itself); (2) that defendants may assert
claims where Fourth Amendment rights are uncertain
(consider the Court’s qualified immunity jurisprudence),
and (3) that sometimes it is difficult to decide the merits of
those uncertain claims. See ante, at 8–9. In fact, the “no
knock” warrants that are provided by many States, by
diminishing uncertainty, may make application of the
knock-and-announce principle less “cost[ly]” on the whole
than application of comparable Fourth Amendment prin
ciples, such as determining whether a particular war
rantless search was justified by exigency. The majority’s
“substantial social costs” argument is an argument
against the Fourth Amendment’s exclusionary principle
itself. And it is an argument that this Court, until now,
has consistently rejected.
III
The majority, Michigan, and the United States make
several additional arguments. In my view, those argu
ments rest upon misunderstandings of the principles
underlying this Court’s precedents.
A
The majority first argues that “the constitutional viola
tion of an illegal manner of entry was not a but-for cause
of obtaining the evidence.” Ante, at 5. But taking causa
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BREYER, J., dissenting

tion as it is commonly understood in the law, I do not see
how that can be so. See W. Keeton, D. Dobbs, R. Keeton,
& D. Owen, Prosser and Keeton on Law of Torts 266 (5th
ed. 1984). Although the police might have entered Hud
son’s home lawfully, they did not in fact do so. Their
unlawful behavior inseparably characterizes their actual
entry; that entry was a necessary condition of their pres
ence in Hudson’s home; and their presence in Hudson’s
home was a necessary condition of their finding and seiz
ing the evidence. At the same time, their discovery of
evidence in Hudson’s home was a readily foreseeable
consequence of their entry and their unlawful presence
within the home. Cf. 2 Restatement (Second) of Torts
§435 (1963–1964).
Moreover, separating the “manner of entry” from the
related search slices the violation too finely. As noted,
Part I–A, supra, we have described a failure to comply
with the knock-and-announce rule, not as an independ
ently unlawful event, but as a factor that renders the
search “constitutionally defective.” Wilson, 514 U. S., at
936; see also id., at 934 (compliance with the knock-and
announce requirement is one of the “factors to be consid
ered in assessing the reasonableness of a search or seizure”
(emphasis added)); Ker v. California, 374 U. S. 23, 53 (1963)
(opinion of Brennan, J.) (“[A] lawful entry is the indispensa
ble predicate of a reasonable search”).
The Court nonetheless accepts Michigan’s argument
that the requisite but-for-causation is not satisfied in this
case because, whether or not the constitutional violation
occurred (what the Court refers to as a “preliminary mis
step”), “the police would have executed the warrant they
had obtained, and would have discovered the gun and
drugs inside the house.” Ante, at 5. As support for this
proposition, Michigan rests on this Court’s inevitable
discovery cases.
This claim, however, misunderstands the inevitable
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BREYER, J., dissenting

discovery doctrine. Justice Holmes in Silverthorne, in
discussing an “independent source” exception, set forth the
principles underlying the inevitable discovery rule. See
supra, at 4. That rule does not refer to discovery that
would have taken place if the police behavior in question
had (contrary to fact) been lawful. The doctrine does not
treat as critical what hypothetically could have happened
had the police acted lawfully in the first place. Rather,
“independent” or “inevitable” discovery refers to discovery
that did occur or that would have occurred (1) despite (not
simply in the absence of) the unlawful behavior and (2)
independently of that unlawful behavior. The government
cannot, for example, avoid suppression of evidence seized
without a warrant (or pursuant to a defective warrant)
simply by showing that it could have obtained a valid
warrant had it sought one. See, e.g., Coolidge v. New
Hampshire, 403 U. S. 443, 450–451 (1971). Instead, it
must show that the same evidence “inevitably would have
been discovered by lawful means.” Nix v. Williams, 467
U. S., at 444 (emphasis added). “What a man could do is
not at all the same as what he would do.” Austin, Ifs And
Cans, 42 Proceedings of the British Academy 109, 111–112
(1956).
The inevitable discovery exception rests upon the prin
ciple that the remedial purposes of the exclusionary rule
are not served by suppressing evidence discovered through
a “later, lawful seizure” that is “genuinely independent of
an earlier, tainted one.” Murray v. United States, 487
U. S. 533, 542 (1988) (emphasis added); see also id., at 545
(Marshall, J., joined by STEVENS and O’Connor, JJ., dis
senting) (“When the seizure of the evidence at issue is
‘wholly independent of’ the constitutional violation, then
exclusion arguably will have no effect on a law enforce
ment officer’s incentive to commit an unlawful search”).
Case law well illustrates the meaning of this principle.
In Nix, supra, police officers violated a defendant’s Sixth
14 HUDSON v. MICHIGAN

BREYER, J., dissenting

Amendment right by eliciting incriminating statements
from him after he invoked his right to counsel. Those
statements led to the discovery of the victim’s body. The
Court concluded that evidence obtained from the victim’s
body was admissible because it would ultimately or inevi
tably have been discovered by a volunteer search party
effort that was ongoing—whether or not the Sixth Amend
ment violation had taken place. Id., at 449. In other
words, the evidence would have been found despite, and
independent of, the Sixth Amendment violation.
In Segura v. United States, 468 U. S. 796 (1984), one of
the “trio of cases” JUSTICE SCALIA says “confirms [the
Court’s] conclusion,” ante, at 13, the Court held that an
earlier illegal entry into an apartment did not require
suppression of evidence that police later seized when
executing a search warrant obtained on the basis of infor
mation unconnected to the initial entry. The Court rea
soned that the “evidence was discovered the day following
the entry, during the search conducted under a valid
warrant”—i.e., a warrant obtained independently without
use of any information found during the illegal entry—and
that “it was the product of that search, wholly unrelated to
the prior [unlawful] entry.” Segura, supra, at 814 (em
phasis added).
In Murray, supra, the Court upheld the admissibility of
seized evidence where agents entered a warehouse with
out a warrant, and then later returned with a valid war
rant that was not obtained on the basis of evidence ob
served during the first (illegal) entry. The Court reasoned
that while the agents’ “[k]nowledge that the marijuana
was in the warehouse was assuredly acquired at the time
of the unlawful entry . . . it was also acquired at the time
of entry pursuant to the warrant, and if that later acquisi
tion was not the result of the earlier entry there is no rea
son why the independent source doctrine should not ap
ply.” Id., at 541 (emphasis added).
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BREYER, J., dissenting

Thus, the Court’s opinion reflects a misunderstanding of
what “inevitable discovery” means when it says, “[i]n this
case, of course, the constitutional violation of an illegal
manner of entry was not a but-for cause of obtaining the
evidence.” Ante, at 5. The majority rests this conclusion
on its next statement: “Whether that preliminary misstep
has occurred or not, the police . . . would have discovered
the gun and the drugs inside the house.” Ibid. Despite
the phrase “of course,” neither of these statements is
correct. It is not true that, had the illegal entry not oc
curred, “police would have discovered the guns and drugs
inside the house.” Without that unlawful entry they
would not have been inside the house; so there would have
been no discovery. See supra, at 12.
Of course, had the police entered the house lawfully,
they would have found the gun and drugs. But that fact is
beside the point. The question is not what police might
have done had they not behaved unlawfully. The question
is what they did do. Was there set in motion an independ
ent chain of events that would have inevitably led to the
discovery and seizure of the evidence despite, and inde
pendent of, that behavior? The answer here is “no.”
B
The majority, Michigan, and the United States point out
that the officers here possessed a warrant authorizing a
search. Ante, at 5. That fact, they argue, means that the
evidence would have been discovered independently or
somehow diminishes the need to suppress the evidence.
But I do not see why that is so. The warrant in question
was not a “no-knock” warrant, which many States (but not
Michigan) issue to assure police that a prior knock is not
necessary. Richards, 520 U. S., at 396, n. 7 (collecting
state statutes). It did not authorize a search that fails to
comply with knock-and-announce requirements. Rather,
it was an ordinary search warrant. It authorized a search
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BREYER, J., dissenting

that complied with, not a search that disregarded, the
Constitution’s knock-and-announce rule.
Would a warrant that authorizes entry into a home on
Tuesday permit the police to enter on Monday? Would a
warrant that authorizes entry during the day authorize
the police to enter during the middle of the night? It is
difficult for me to see how the presence of a warrant that
does not authorize the entry in question has anything to
do with the “inevitable discovery” exception or otherwise
diminishes the need to enforce the knock-and-announce
requirement through suppression.
C
The majority and the United States set forth a policy-
related variant of the causal connection theme: The
United States argues that the law should suppress evi
dence only insofar as a Fourth Amendment violation
causes the kind of harm that the particular Fourth
Amendment rule seeks to protect against. It adds that the
constitutional purpose of the knock-and-announce rule is
to prevent needless destruction of property (such as break
ing down a door) and to avoid unpleasant surprise. And it
concludes that the exclusionary rule should suppress
evidence of, say, damage to property, the discovery of a
defendant in an “intimate or compromising moment,” or
an excited utterance from the occupant caught by surprise,
but nothing more. Brief for United States as Amicus
Curiae 12, 28.
The majority makes a similar argument. It says that
evidence should not be suppressed once the causal connec
tion between unlawful behavior and discovery of the evi
dence becomes too “attenuated.” Ante, at 5. But the ma
jority then makes clear that it is not using the word
“attenuated” to mean what this Court’s precedents have
typically used that word to mean, namely, that the discov
ery of the evidence has come about long after the unlawful
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BREYER, J., dissenting

behavior took place or in an independent way, i.e., through
“ ‘means sufficiently distinguishable to be purged of the
primary taint.’ ” Wong Sun v. United States, 371 U. S. 471,
487–488 (1963); see Brown v. Illinois, 422 U. S. 590, 603–
604 (1975).
Rather, the majority gives the word “attenuation” a new
meaning (thereby, in effect, making the same argument as
the United States). “Attenuation,” it says, “also occurs
when, even given a direct causal connection, the interest
protected by the constitutional guarantee that has been
violated would not be served by suppression of the evi
dence obtained.” Ante, at 6. The interests the knock-and
announce rule seeks to protect, the Court adds, are “hu
man life” (at stake when a householder is “surprised”),
“property” (such as the front door), and “those elements of
privacy and dignity that can be destroyed by a sudden
entrance,” namely, “the opportunity to collect oneself
before answering the door.” Ante, at 7. Since none of
those interests led to the discovery of the evidence seized
here, there is no reason to suppress it.
There are three serious problems with this argument.
First, it does not fully describe the constitutional values,
purposes, and objectives underlying the knock-and
announce requirement. That rule does help to protect
homeowners from damaged doors; it does help to protect
occupants from surprise. But it does more than that. It
protects the occupants’ privacy by assuring them that
government agents will not enter their home without
complying with those requirements (among others) that
diminish the offensive nature of any such intrusion. Many
years ago, Justice Frankfurter wrote for the Court that
the “knock at the door, . . . as a prelude to a search, with
out authority of law . . . [is] inconsistent with the concep
tion of human rights enshrined in [our] history” and Con
stitution. Wolf, 338 U. S., at 28. How much the more
offensive when the search takes place without any knock
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BREYER, J., dissenting

at all. Cf. Wilson, 514 U. S., at 931 (knock-and-announce
rule recognizes that “the common law generally protected
a man’s house as ‘his castle of defence and asylum’ ” (quot
ing 3 W. Blackstone, Commentaries *288)); Miller, 357
U. S., at 313 (federal knock-and-announce statute “codi
f[ied] a tradition embedded in Anglo-American law” that
reflected “the reverence of the law for the individual’s
right of privacy in his house”).
Over a century ago this Court wrote that “it is not the
breaking of his doors” that is the “essence of the offence,”
but the “invasions on the part of the government . . . of the
sanctity of a man’s home and the privacies of life.” Boyd,
116 U. S., at 630. And just this Term we have reiterated
that “it is beyond dispute that the home is entitled to
special protection as the center of the private lives of our
people.” Georgia v. Randolph, 547 U. S. ___, ___ (2006)
(slip op., at 10) (quoting Minnesota v. Carter, 525 U. S. 83,
99 (1998) (KENNEDY, J., concurring)). The knock-and
announce requirement is no less a part of the “centuries
old principle” of special protection for the privacy of the
home than the warrant requirement. See 547 U. S., at ___
(slip op., at 10) (citing Miller, supra, at 307). The Court is
therefore wrong to reduce the essence of its protection to
“the right not to be intruded upon in one’s nightclothes.”
Ante, at 10; see Richards, 520 U. S., at 393, n. 5
(“[I]ndividual privacy interest[s]” protected by the rule
are “not inconsequential” and “should not be unduly
minimized”).
Second, whether the interests underlying the knock-
and-announce rule are implicated in any given case is, in a
sense, beside the point. As we have explained, failure to
comply with the knock-and-announce rule renders the
related search unlawful. Wilson, supra, at 936. And
where a search is unlawful, the law insists upon suppres
sion of the evidence consequently discovered, even if that
evidence or its possession has little or nothing to do with
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BREYER, J., dissenting

the reasons underlying the unconstitutionality of a search.
The Fourth Amendment does not seek to protect contra
band, yet we have required suppression of contraband
seized in an unlawful search. See, e.g., Kyllo v. United
States, 533 U. S. 27, 40 (2001); Coolidge, 403 U. S., at 473.
That is because the exclusionary rule protects more gen
eral “privacy values through deterrence of future police
misconduct.” James v. Illinois, 493 U. S. 307, 319 (1990).
The same is true here.
Third, the majority’s interest-based approach departs
from prior law. Ordinarily a court will simply look to see
if the unconstitutional search produced the evidence. The
majority does not refer to any relevant case in which,
beyond that, suppression turned on the far more detailed
relation between, say, (1) a particular materially false
statement made to the magistrate who issued a (conse
quently) invalid warrant and (2) evidence found after a
search with that warrant. But cf. ante, at 15, n. 2 (plural
ity opinion) (citing New York v. Harris, 495 U. S. 14
(1990), as such a case in section of opinion that JUSTICE
KENNEDY does not join). And the majority’s failure does
not surprise me, for such efforts to trace causal connec
tions at retail could well complicate Fourth Amendment
suppression law, threatening its workability.
D
The United States, in its brief and at oral argument, has
argued that suppression is “an especially harsh remedy
given the nature of the violation in this case.” Brief for
United States as Amicus Curiae 28; see also id., at 24.
This argument focuses upon the fact that entering a house
after knocking and announcing can, in some cases, prove
dangerous to a police officer. Perhaps someone inside has
a gun, as turned out to be the case here. The majority
adds that police officers about to encounter someone who
may try to harm them will be “uncertain” as to how long to
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BREYER, J., dissenting

wait. Ante, at 9. It says that, “[i]f the consequences of
running afoul” of the knock-and-announce “rule were so
massive,” i.e., would lead to the exclusion of evidence, then
“officers would be inclined to wait longer than the law
requires—producing preventable violence against officers
in some cases.” Ante, at 8–9.
To argue that police efforts to assure compliance with
the rule may prove dangerous, however, is not to argue
against evidence suppression. It is to argue against the
validity of the rule itself. Similarly, to argue that en
forcement means uncertainty, which in turn means the
potential for dangerous and longer-than-necessary delay,
is (if true) to argue against meaningful compliance with
the rule.
The answer to the first argument is that the rule itself
does not require police to knock or to announce their pres
ence where police have a “reasonable suspicion” that doing
so “would be dangerous or futile” or “would inhibit the
effective investigation of the crime by, for example, allow
ing the destruction of evidence.” Richards, supra, at 394;
see Banks, 540 U. S., at 36–37; Wilson, supra, at 935–936.
The answer to the second argument is that States can,
and many do, reduce police uncertainty while assuring a
neutral evaluation of concerns about risks to officers or the
destruction of evidence by permitting police to obtain a
“no-knock” search warrant from a magistrate judge,
thereby assuring police that a prior announcement is not
necessary. Richards, 520 U. S., at 396, n. 7 (collecting
state statutes). While such a procedure cannot remove all
uncertainty, it does provide an easy way for officers to
comply with the knock-and-announce rule.
Of course, even without such a warrant, police maintain
the backup “authority to exercise independent judgment
concerning the wisdom of a no-knock entry at the time the
warrant is being executed.” Ibid. “[I]f circumstances
support a reasonable suspicion of exigency when the offi
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BREYER, J., dissenting

cers arrive at the door, they may go straight in.” Banks,
supra, at 37. And “[r]easonable suspicion is a less de
manding standard than probable cause . . . .” Alabama v.
White, 496 U. S. 325, 330 (1990); see Terry v. Ohio, 392
U. S. 1, 21–22 (1968) (no Fourth Amendment violation
under the reasonable suspicion standard if “the facts
available to the officer at the moment of the seizure or the
search ‘warrant a man of reasonable caution in the belief’
that the action taken was appropriate”).
Consider this very case. The police obtained a search
warrant that authorized a search, not only for drugs, but
also for guns. App. 5. If probable cause justified a search
for guns, why would it not also have justified a no-knock
warrant, thereby diminishing any danger to the officers?
Why (in a State such as Michigan that lacks no-knock
warrants) would it not have justified the very no-knock
entry at issue here? Indeed, why did the prosecutor not
argue in this very case that, given the likelihood of guns,
the no-knock entry was lawful? From what I have seen in
the record, he would have won. And had he won, there
would have been no suppression here.
That is the right way to win. The very process of argu
ing the merits of the violation would help to clarify the
contours of the knock-and-announce rule, contours that
the majority believes are too fuzzy. That procedural fact,
along with no-knock warrants, back up authority to enter
without knocking regardless, and use of the “reasonable
suspicion” standard for doing so should resolve the gov
ernment’s problems with the knock-and-announce rule
while reducing the “uncertain[ty]” that the majority dis
cusses to levels beneath that found elsewhere in Fourth
Amendment law (e.g., exigent circumstances). Ante, at 8.
Regardless, if the Court fears that effective enforcement of
a constitutional requirement will have harmful conse
quences, it should face those fears directly by addressing
the requirement itself. It should not argue, “the require
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BREYER, J., dissenting

ment is fine, indeed, a serious matter, just don’t enforce
it.”
E
It should be apparent by now that the three cases upon
which JUSTICE SCALIA relies—Segura v. United States,
468 U. S. 796; New York v. Harris, 495 U. S. 14; and Ra
mirez, 523 U. S. 65—do not support his conclusion. See
ante, at 13–15. Indeed, JUSTICE KENNEDY declines to join
this section of the lead opinion because he fails to see the
relevance of Segura and Harris, though he does rely on
Ramirez. Ante, at 3 (opinion concurring in part and con
curring in judgment).
JUSTICE SCALIA first argues that, if the “search in
Segura could be ‘wholly unrelated to the prior entry, . . .
when the only entry was warrantless, it would be bizarre
to treat more harshly the actions in this case, where the
only entry was with a warrant.” Ante, at 14. Then it says
that, “[i]f the probable cause backing a warrant that was
issued later in time could be an ‘independent source’ for a
search that proceeded after the officers illegally entered
and waited, a search warrant obtained before going in
must have at least this much effect.” Ibid. I do not under
stand these arguments. As I have explained, the presence
of a warrant that did not authorize a search that fails to
comply with knock-and-announce requirements is beside
the point. See Part III–B, supra. And the timing of the
warrant in Segura made no difference to the case. The
relevant fact about the warrant there was that it was
lawfully obtained and arguably set off an independent
chain of events that led the police to seize the evidence.
468 U. S., at 814; see also id., at 814–815 (“The valid
warrant search was a ‘means sufficiently distinguishable’
to purge the evidence of any ‘taint’ arising from the entry”
(citations omitted)). As noted, there is no such independ
ent event, or intervening chain of events that would purge
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BREYER, J., dissenting

the taint of the illegal entry, present here. See supra, at
15. The search that produced the relevant evidence here
is the very search that the knock-and-announce violation
rendered unlawful. There simply is no “independent
source.”
As importantly, the Court in Segura said nothing to
suggest it intended to create a major exclusionary rule
exception, notwithstanding the impact of such an excep
tion on deterrence. Indeed, such an exception would be
inconsistent with a critical rationale underlying the inde
pendent source and inevitable discovery rules, which was
arguably available in Segura, and which is clearly absent
here. That rationale concerns deterrence. The threat of
inadmissibility deters unlawful police behavior; and the
existence of an exception applicable where evidence is
found through an untainted independent route will rarely
undercut that deterrence. That is because the police can
rarely rely upon such an exception—at least not often
enough to change the deterrence calculus. See Murray,
487 U. S., at 540 (“We see the incentives differently. An
officer with probable cause sufficient to obtain a search
warrant would be foolish to enter the premises in an
unlawful manner. By doing so, he would risk suppression
of all evidence on the premises . . . ”); Nix, 467 U. S., at
445 (“A police officer who is faced with the opportunity to
obtain evidence illegally will rarely, if ever, be in a posi
tion to calculate whether the evidence sought would inevi
tably be discovered”); id., at 444 (“If the prosecution can
establish by a preponderance of the evidence that the
information ultimately or inevitably would have been
discovered by lawful means—here the volunteers’ search—
then the deterrence rationale has so little basis that the
evidence should be received”).
Segura’s police officers would have been foolish to have
entered the apartment unlawfully with the ex ante hope
that an independent causal chain of events would later
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BREYER, J., dissenting

occur and render admissible the evidence they found. By
way of contrast, today’s holding will seriously undermine
deterrence in knock-and-announce cases. Officers will
almost always know ex ante that they can ignore the
knock-and-announce requirement without risking the
suppression of evidence discovered after their unlawful
entry. That fact is obvious, and this Court has never
before today—not in Segura or any other post-Weeks (or
post-Mapp) case—refused to apply the exclusionary rule
where its absence would so clearly and so significantly
impair government officials’ incentive to comply with
comparable Fourth Amendment requirements.
Neither does New York v. Harris, supra, support the
Court’s result. See ante, at 6, 14; but see ante, at 3 (opin
ion of KENNEDY, J.) (declining to join section relying on
Harris). In Harris, police officers arrested the defendant
at his home without a warrant, in violation of Payton v.
New York, 445 U. S. 573 (1980). Harris made several
incriminating statements: a confession in his home, a
written inculpatory statement at the stationhouse, and a
videotaped interview conducted by the district attorney at
the stationhouse. 495 U. S., at 16. The trial court sup
pressed the statements given by Harris in the house and
on the videotape, and the State did not challenge either of
those rulings. Ibid. The sole question in the case was
whether the written statement given later at the station-
house should also have been suppressed. The Court held
that this later, outside-the-home statement “was admissi
ble because Harris was in legal custody . . . and because
the statement, while the product of an arrest and being in
custody, was not the fruit of the fact that the arrest was
made in the house rather than someplace else.” Id., at 20.
Immediately after the Court stated its holding, it ex
plained:
“To put the matter another way, suppressing the
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BREYER, J., dissenting

statement taken outside the house would not serve
the purpose of the rule that made Harris’ in-house ar
rest illegal. The warrant requirement for an arrest in
the home is imposed to protect the home, and anything
incriminating the police gathered from arresting Har
ris in his home, rather than elsewhere, has been ex
cluded, as it should have been; the purpose of the rule
has thereby been vindicated.” Ibid. (emphasis added).
How can JUSTICE SCALIA maintain that the evidence
here—a gun and drugs seized in the home—is “ ‘not the
fruit’ ” of the illegal entry? Ante, at 14. The officers’ fail
ure to knock and announce rendered the entire search
unlawful, Wilson, 514 U. S., at 936, and that unlawful
search led to the discovery of evidence in petitioner’s
home. Thus, Harris compels the opposite result than that
reached by the Court today. Like the Payton rule at issue
in Harris, the knock-and-announce rule reflects the “rev
erence of the law for the individual’s right of privacy in his
house.” Miller, 357 U. S., at 313; cf. Harris, 495 U. S., at
17 (“Payton itself emphasized that our holding in that case
stemmed from the ‘overriding respect for the sanctity of
the home that has been embedded in our traditions since
the origins of the Republic’ ”). Like the confession that was
“excluded, as it should have been,” in Harris, id., at 20, the
evidence in this case was seized in the home, immediately
following the illegal entry. And like Harris, nothing in
petitioner’s argument would require the suppression of
evidence obtained outside the home following a knock-and
announce violation should be suppressed, precisely be
cause officers have a remaining incentive to follow the rule
to avoid the suppression of any evidence obtained from the
very place they are searching. Cf. ibid. (“Even though we
decline to suppress statements made outside the home
following a Payton violation, the principle incentive to
obey Payton still obtains: the police know that a war
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BREYER, J., dissenting

rantless entry will lead to the suppression of any evidence
found, or statements taken, inside the home”).
I concede that United States v. Ramirez, 523 U. S. 65,
offers the majority its last best hope. Ante, at 14–15. But
not even that case can offer the majority significant sup
port. The majority focuses on the Court’s isolated state
ment that “destruction of property in the course of a
search may violate the Fourth Amendment, even though
the entry itself is lawful and the fruits of the search are not
subject to suppression.” Ramirez, supra, at 71 (emphasis
added). But even if I accept this dictum, the entry here is
unlawful, not lawful. Wilson, 514 U. S., at 931, 934. It is
one thing to say (in an appropriate case) that destruction
of property after proper entry has nothing to do with
discovery of the evidence, and to refuse to suppress. It
would be quite another thing to say that improper entry
had nothing to do with discovery of the evidence in this
case. Moreover, the deterrence analysis for the property
destruction cases (where, by definition, there will almost
always be quantifiable damages) might well differ.
IV
There is perhaps one additional argument implicit in
the majority’s approach. The majority says, for example,
that the “cost” to a defendant of “entering this lottery,” i.e.,
of claiming a “knock-and-announce” violation, “would be
small, but the jackpot enormous”—namely, a potential
“get-out-of-jail-free card.” Ante, at 8. It adds that the
“social costs” of applying the exclusionary rule here are
not worth the deterrence benefits. Ante, at 13. Leaving
aside what I believe are invalid arguments based on
precedent or the majority’s own estimate that suppression
is not necessary to deter constitutional violations, one is
left with a simple unvarnished conclusion, namely, that in
this kind of case, a knock-and-announce case, “[r]esort to
the massive remedy of suppressing evidence of guilt is
 Cite as: 547 U. S. ____ (2006) 27

BREYER, J., dissenting

unjustified.” Ibid. Why is that judicial judgment, taken
on its own, inappropriate? Could it not be argued that the
knock-and-announce rule, a subsidiary Fourth Amend
ment rule, is simply not important enough to warrant a
suppression remedy? Could the majority not simply claim
that the suppression game is not worth the candle?
The answer, I believe, is “no.” That “no” reflects history,
a history that shows the knock-and-announce rule is
important. See Wilson, supra, at 931–936. That “no”
reflects precedent, precedent that shows there is no pre
existing legal category of exceptions to the exclusionary
rule into which the knock-and-announce cases might fit.
See supra, at 8–9. That “no” reflects empirical fact, ex
perience that provides confirmation of what common sense
suggests: without suppression there is little to deter
knock-and-announce violations. See supra, at 6–7.
There may be instances in the law where text or history
or tradition leaves room for a judicial decision that rests
upon little more than an unvarnished judicial instinct.
But this is not one of them. Rather, our Fourth Amend
ment traditions place high value upon protecting privacy
in the home. They emphasize the need to assure that its
constitutional protections are effective, lest the Amend
ment ‘sound the word of promise to the ear but break it to
the hope.’ They include an exclusionary principle, which
since Weeks has formed the centerpiece of the criminal
law’s effort to ensure the practical reality of those prom
ises. That is why the Court should assure itself that any
departure from that principle is firmly grounded in logic,
in history, in precedent, and in empirical fact. It has not
done so. That is why, with respect, I dissent.
28 HUDSON v. MICHIGAN

Appendix to opinion of BREYER, J.

APPENDIX TO OPINION OF BREYER, J.
Fourth Amendment decisions from 1914 to present
requiring suppression of evidence seized (or remanding for
lower court to make suppression determination) in a pri
vate home following an illegal arrest or search:
1. eeks v. United States, 232 U. S. 383 (1914) (war
W
rantless search)
2. mos v. United States, 255 U. S. 313 (1921) (war
A
rantless arrest and search)
3. gnello v. United States, 269 U. S. 20 (1925) (war
A
rantless search)
4. yars v. United States, 273 U. S. 28 (1927) (inva
B
lid warrant)
5. nited States v. Berkeness, 275 U. S. 149 (1927)
U
(invalid warrant; insufficient affidavit)
6. aylor v. United States, 286 U. S. 1 (1932) (war
T
rantless search)
7. rau v. United States, 287 U. S. 124 (1932) (inva
G
lid warrant; insufficient affidavit)
8. athanson v. United States, 290 U. S. 41 (1933)
N
(invalid warrant; insufficient affidavit)
9. cDonald v. United States, 335 U. S. 451 (1948)
M
(warrantless arrest and search)
10. Kremen v. United States, 353 U. S. 346 (1957) (per
curiam) (warrantless search)
11. Elkins v. United States, 364 U. S. 206 (1960)
(search beyond scope of warrant)
12. Silverman v. United States, 365 U. S. 505 (1961)
(warrantless use of electronic device)
13. Chapman v. United States, 365 U. S. 610 (1961)
(warrantless search)
14. Mapp v. Ohio, 367 U. S. 643 (1961) (warrantless
search)
15. Wong Sun v. United States, 371 U. S. 471 (1963)
(warrantless search and arrest)
 Cite as: 547 U. S. ____ (2006) 29

Appendix to opinion of BREYER, J.

16. Fahy v. Connecticut, 375 U. S. 85 (1963) (war
rantless search)
17. Aguilar v. Texas, 378 U. S. 108 (1964) (invalid
warrant; insufficient affidavit)
18. Stanford v. Texas, 379 U. S. 476 (1965) (invalid
warrant; particularity defect)
19. James v. Louisiana, 382 U. S. 36 (1965) (per cu
riam) (warrantless search)
20. Riggan v. Virginia, 384 U. S. 152 (1966) (per cu
riam) (invalid warrant; insufficient affidavit)
21. Bumper v. North Carolina, 391 U. S. 543 (1968)
(lack of valid consent to search)
22. Recznik v. City of Lorain, 393 U. S. 166 (1968)
(per curiam) (warrantless search)
23. Chimel v. California, 395 U. S. 752 (1969) (invalid
search incident to arrest)
24. Von Cleef v. New Jersey, 395 U. S. 814 (1969) (per
curiam) (invalid search incident to arrest)
25. Shipley v. California, 395 U. S. 818 (1969) (per
curiam) (invalid search incident to arrest)
26. Vale v. Louisiana, 399 U. S. 30 (1970) (invalid
search incident to arrest)
27. Connally v. Georgia, 429 U. S. 245 (1977) (per cu
riam) (invalid warrant; magistrate judge not neu
tral)
28. Michigan v. Tyler, 436 U. S. 499 (1978) (war
rantless search)
29. Mincey v. Arizona, 437 U. S. 385 (1978) (war
rantless search)
30. Franks v. Delaware, 438 U. S. 154 (1978) (invalid
warrant; obtained through perjury)
31. Payton v. New York, 445 U. S. 573 (1980) (war
rantless arrest)
32. Steagald v. United States, 451 U. S. 204 (1981)
(warrantless search)
33. Michigan v. Clifford, 464 U. S. 287 (1984) (war
30 HUDSON v. MICHIGAN

Appendix to opinion of BREYER, J.

rantless search)
34. Welsh v. Wisconsin, 466 U. S. 740 (1984) (war
rantless entry into home without exigent circum
stances)
35. Thompson v. Louisiana, 469 U. S. 17 (1984) (per
curiam) (warrantless search)
36. Arizona v. Hicks, 480 U. S. 321 (1987) (unreason
able search)
37. Minnesota v. Olson, 495 U. S. 91 (1990) (war
rantless entry into home)
38. Flippo v. West Virginia, 528 U. S. 11 (1999) (per
curiam) (warrantless search)
39. Kyllo v. United States, 533 U. S. 27 (2001) (war
rantless use of heat-imaging technology)
40. Kirk v. Louisiana, 536 U. S. 635 (2002) (per cu
riam) (warrantless arrest and search)
41. Kaupp v. Texas, 538 U. S. 626 (2003) (per curiam)
(warrantless search)