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

2 HUDSON v. MICHIGAN

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.

Cite as: 547 U. S. ____ (2006) 1

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

Cite as: 547 U. S. ____ (2006) 3

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

4 HUDSON v. MICHIGAN

Opinion of the Court

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

Cite as: 547 U. S. ____ (2006) 5

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

6 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 7

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.

8 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 9

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

10 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 11

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

12 HUDSON v. MICHIGAN

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

12 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 13

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).

Cite as: 547 U. S. ____ (2006) 15

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

16 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 17

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

18 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 19

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

20 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 21

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

22 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 23

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

24 HUDSON v. MICHIGAN

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

Cite as: 547 U. S. ____ (2006) 25

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

26 HUDSON v. MICHIGAN

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)