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, Washington,
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. 11–564

															_________________

															FLORIDA, PETITIONER v. JOELIS
JARDINES

															on writ of certiorari to the supreme court of
florida

															[March 26, 2013]

															Justice Scalia delivered the opinion of the
Court.

															We consider whether using a drug-sniffing dog on
a homeowner’s porch to investigate the contents of the home is a
“search” within the meaning of the Fourth Amendment.

															I

															In 2006, Detective William Pedraja of the
Miami-Dade Police Department received an unverified tip that mari-
juana was being grown in the home of respondent Joelis Jardines.
One month later, the Department and the Drug Enforcement
Administration sent a joint surveillance team to Jardines’ home.
Detective Pedraja was part of that team. He watched the home for
fifteen minutes and saw no vehicles in the driveway or activity
around the home, and could not see inside because the blinds were
drawn. Detective Pedraja then approached Jardines’ home accompanied
by Detective Douglas Bartelt, a trained canine handler who had just
arrived at the scene with his drug-sniffing dog. The dog was
trained to detect the scent of marijuana, cocaine, heroin, and
several other drugs, indicating the presence of any of these
substances through particular behavioral changes recognizable by
his handler.

															Detective Bartelt had the dog on a six-foot
leash, owing in part to the dog’s “wild” nature, App. to Pet. for
Cert. A–35, and tendency to dart around erratically while
searching. As the dog approached Jardines’ front porch, he
apparently sensed one of the odors he had been trained to detect,
and began energetically exploring the area for the strongest point
source of that odor. As Detective Bartelt explained, the dog “began
tracking that airborne odor by . . . tracking back and
forth,” engaging in what is called “bracketing,” “back and forth,
back and forth.” Id., at A– 33 to A–34. Detective Bartelt
gave the dog “the full six feet of the leash plus whatever safe
distance [he could] give him” to do this—he testified that he
needed to give the dog “as much distance as I can.” Id., at
A–35. And Detective Pedraja stood back while this was occurring, so
that he would not “get knocked over” when the dog was “spinning
around trying to find” the source. Id., at A–38.

															After sniffing the base of the front door, the
dog sat, which is the trained behavior upon discovering the odor’s
strongest point. Detective Bartelt then pulled the dog away from
the door and returned to his vehicle. He left the scene after
informing Detective Pedraja that there had been a positive alert
for narcotics.

															On the basis of what he had learned at the home,
De- tective Pedraja applied for and received a warrant to search
the residence. When the warrant was executed later that day,
Jardines attempted to flee and was arrested; the search revealed
marijuana plants, and he was charged with trafficking in
cannabis.

															At trial, Jardines moved to suppress the
marijuana plants on the ground that the canine investigation was an
unreasonable search. The trial court granted the motion, and the
Florida Third District Court of Appeal reversed. On a petition for
discretionary review, the Florida Supreme Court quashed the
decision of the Third District Court of Appeal and approved the
trial court’s decision to suppress, holding (as relevant here) that
the use of the trained narcotics dog to investigate Jardines’ home
was a Fourth Amendment search unsupported by probable cause,
rendering invalid the warrant based upon information gathered in
that search. 73 So. 3d 34 (2011).

															We granted certiorari, limited to the question
of whether the officers’ behavior was a search within the meaning
of the Fourth Amendment. 565 U. S. ___ (2012).

															II

															The Fourth Amendment provides in relevant part
that the “right of the people to be secure in their persons,
houses, papers, and effects, against unreasonable searches and
seizures, shall not be violated.” The Amendment establishes a
simple baseline, one that for much of our history formed the
exclusive basis for its protections: When “the Government obtains
information by physically intruding” on persons, houses, papers, or
effects, “a ‘search’ within the original meaning of the Fourth
Amendment” has “un- doubtedly occurred.” United States v. Jones , 565 U. S. ___, ___, n. 3 (2012) (slip op.,
at 6, n. 3). By reason of our decision in Katz v. United States , 389 U.S.
347 (1967), property rights “are not the sole measure of Fourth
Amendment violations,” Soldal v. Cook County , 506 U.S.
56 , 64 (1992)—but though Katz may add to the baseline,
it does not subtract anything from the Amendment’s protections
“when the Government does engage in [a] physi- cal intrusion
of a constitutionally protected area,” United States v. Knotts , 460 U.S.
276 , 286 (1983) (Brennan, J., concurring in the judgment).

															That principle renders this case a
straightforward one. The officers were gathering information in an
area belonging to Jardines and immediately surrounding his house—in
the curtilage of the house, which we have held enjoys protection as
part of the home itself. And they gathered that information by
physically entering and occupying the area to engage in conduct not
explicitly or implicitly permitted by the homeowner.

															A

															The Fourth Amendment “indicates with some
precision the places and things encompassed by its protections”:
persons, houses, papers, and effects. Oliver v. United
States , 466 U.S.
170 , 176 (1984). The Fourth Amendment does not, therefore,
prevent all investigations conducted on private property; for
example, an officer may (subject to Katz ) gather information
in what we have called “open fields”—even if those fields are
privately owned—because such fields are not enumerated in the
Amendment’s text. Hester v. United States , 265 U.S.
57 (1924).

															But when it comes to the Fourth Amendment, the
home is first among equals. At the Amendment’s “very core” stands
“the right of a man to retreat into his own home and there be free
from unreasonable governmental in- trusion.” Silverman v. United States , 365 U.S.
505 , 511 (1961). This right would be of little practical value
if the State’s agents could stand in a home’s porch or side garden
and trawl for evidence with impunity; the right to retreat would be
significantly diminished if the police could enter a man’s property
to observe his repose from just outside the front window.

															We therefore regard the area “immediately
surrounding and associated with the home”—what our cases call the
curtilage—as “part of the home itself for Fourth Amendment
purposes.” Oliver , supra, at 180. That principle has
ancient and durable roots. Just as the distinction between the home
and the open fields is “as old as the common law,” Hester , supra, at 59, so too is the identity of home and what
Blackstone called the “curtilage or homestall,” for the “house
protects and privileges all its branches and appurtenants.” 4 W.
Blackstone, Commentaries on the Laws of England 223, 225 (1769).
This area around the home is “intimately linked to the home, both
physically and psychologically,” and is where “privacy expectations
are most heightened.” California v. Ciraolo , 476 U.S.
207 , 213 (1986).

															While the boundaries of the curtilage are
generally “clearly marked,” the “conception defining the curtilage”
is at any rate familiar enough that it is “easily understood from
our daily experience.” Oliver , 466 U. S., at 182,
n. 12. Here there is no doubt that the officers entered it:
The front porch is the classic exemplar of an area adjacent to the
home and “to which the activity of home life extends.” Ibid. B

															Since the officers’ investigation took place
in a constitutionally protected area, we turn to the question of
whether it was accomplished through an unlicensed physical in-
trusion.[ 1 ] While law
enforcement officers need not “shield their eyes” when passing by
the home “on public thoroughfares,” Ciraolo , 476 U. S.,
at 213, an officer’s leave to gather information is sharply
circumscribed when he steps off those thoroughfares and enters the
Fourth Amendment’s protected areas. In permitting, for example,
visual observation of the home from “public navigable airspace,” we
were careful to note that it was done “in a physically nonintrusive
manner.” Ibid. Entick v. Carrington , 2 Wils.
K. B. 275, 95 Eng. Rep. 807 (K. B. 1765), a case “undoubtedly
familiar” to “every American statesman” at the time of the
Founding, Boyd v. United States , 116 U.S.
616 , 626 (1886), states the general rule clearly: “[O]ur law
holds the property of every man so sacred, that no man can set his
foot upon his neighbour’s close without his leave.” 2 Wils. K. B.,
at 291, 95 Eng. Rep., at 817. As it is undisputed that the
detectives had all four of their feet and all four of their
companion’s firmly planted on the constitutionally protected
extension of Jardines’ home, the only question is whether he had
given his leave (even implicitly) for them to do so. He had
not.

															“A license may be implied from the habits of the
country,” notwithstanding the “strict rule of the English common
law as to entry upon a close.” McKee v. Gratz , 260 U.S.
127 , 136 (1922) (Holmes, J.). We have accordingly recognized
that “the knocker on the front door is treated as an invitation or
license to attempt an entry, justifying ingress to the home by
solicitors, hawkers and peddlers of all kinds.” Breard v. Alexandria , 341 U.S.
622 , 626 (1951). This implicit license typically permits the
visitor to approach the home by the front path, knock promptly,
wait briefly to be received, and then (absent invitation to linger
longer) leave. Complying with the terms of that traditional
invitation does not require fine-grained legal knowledge; it is
generally managed without incident by the Nation’s Girl Scouts and
trick-or-treaters.[ 2 ] Thus, a
police officer not armed with a warrant may approach a home and
knock, precisely because that is “no more than any private citizen
might do.” Kentucky v. King , 563 U. S. ___, ___
(2011) (slip op., at 16).

															But introducing a trained police dog to explore
the area around the home in hopes of discovering incriminating
evidence is something else. There is no customary invitation to do that . An invitation to engage in canine forensic
investigation assuredly does not inhere in the very act of hanging
a knocker.[ 3 ] To find a visitor
knocking on the door is routine (even if sometimes unwelcome); to
spot that same visitor exploring the front path with a metal
detector, or marching his bloodhound into the garden before saying
hello and asking permission, would inspire most of us to—well, call
the police. The scope of a license—express or implied—is limited
not only to a particular area but also to a specific purpose.
Consent at a traffic stop to an officer’s checking out an anonymous
tip that there is a body in the trunk does not permit the officer
to rummage through the trunk for narcotics. Here, the background
social norms that invite a visitor to the front door do not invite
him there to conduct a search.[ 4 ]

															The State points to our decisions holding that
the subjective intent of the officer is irrelevant. See Ashcroft v. al-Kidd , 563 U. S. ___ (2011); Whren v. United States , 517 U.S.
806 (1996). But those cases merely hold that a stop or search that is objectively reasonable is not vitiated by the fact
that the officer’s real reason for making the stop or search has
nothing to do with the validating reason. Thus, the defendant will
not be heard to complain that although he was speeding the
officer’s real reason for the stop was racial harassment. See id., at 810, 813. Here, however, the question before the
court is precisely whether the officer’s conduct was an
objectively reasonable search. As we have described, that depends
upon whether the officers had an implied license to enter the
porch, which in turn depends upon the purpose for which they
entered. Here, their behavior objectively reveals a purpose to
conduct a search, which is not what anyone would think he had
license to do.

															III

															The State argues that investigation by a
forensic narcotics dog by definition cannot implicate any
legitimate privacy interest. The State cites for authority our
decisions in United States v. Place , 462 U.S.
696 (1983), United States v. Jacobsen , 466 U.S.
109 (1984), and Illinois v. Caballes , 543 U.S.
405 (2005), which held, respectively, that canine inspection of
luggage in an airport, chemical testing of a substance that had
fallen from a parcel in transit, and canine inspection of an
automobile during a lawful traffic stop, do not violate the
“reasonable expectation of privacy” described in Katz. Just last Term, we considered an argument much
like this. Jones held that tracking an automobile’s where-
abouts using a physically-mounted GPS receiver is a Fourth
Amendment search. The Government argued that the Katz standard “show[ed] that no search occurred,” as the defendant had
“no ‘reasonable expectation of privacy’ ” in his whereabouts
on the public roads, Jones , 565 U. S., at ___ (slip
op., at 5)—a proposition with at least as much support in our case
law as the one the State marshals here. See, e.g., United
States v. Knotts , 460 U.S.
276 , 278 (1983). But because the GPS receiver had been
physically mounted on the defendant’s automobile (thus intruding on
his “effects”), we held that tracking the vehicle’s movements was a
search: a person’s “ Fourth Amendment rights do not rise or fall
with the Katz formulation.” Jones , supra, at
___ (slip op., at 5). The Katz reasonable-expectations test
“has been added to , not substituted for ,” the
traditional property-based understanding of the Fourth Amendment,
and so is unnecessary to consider when the government gains
evidence by physically intruding on constitutionally protected
areas. Jones , supra , at ___ (slip op., at 8).

															Thus, we need not decide whether the officers’
investigation of Jardines’ home violated his expectation of privacy
under Katz . One virtue of the Fourth Amendment’s
property-rights baseline is that it keeps easy cases easy. That the
officers learned what they learned only by physically intruding on
Jardines’ property to gather evidence is enough to establish that a
search occurred.

															For a related reason we find irrelevant the
State’s argument (echoed by the dissent) that forensic dogs have
been commonly used by police for centuries. This argument is
apparently directed to our holding in Kyllo v. United
States , 533 U.S.
27 (2001), that surveillance of the home is a search where “the
Government uses a device that is not in general public use” to
“explore details of the home that would previously have been
unknowable without physical intrusion .” Id. , at 40
(emphasis added). But the implication of that statement
( inclusio unius est exclusio alterius ) is that when the
government uses a physical intrusion to explore details of the home
(including its curtilage), the antiquity of the tools that they
bring along is irrelevant.

															*  *  *

															The government’s use of trained police dogs to
inves- tigate the home and its immediate surroundings is a “search”
within the meaning of the Fourth Amendment. The judgment of the
Supreme Court of Florida is therefore affirmed.

															It is so ordered. Notes 1 At oral argument, the
State and its amicus the Solicitor General argued that
Jardines conceded in the lower courts that the officers had a right
to be where they were. This misstates the record. Jardines conceded
nothing more than the unsurprising proposition that the of-ficers
could have lawfully approached his home to knock on the front door
in hopes of speaking with him. Of course, that is not what they
did. 2 With this much, the
dissent seems to agree—it would inquire into “ ‘the appearance
of things,’ ” post, at 5 (opinion of Alito, J.), what
is “typica[l]” for a visitor, ibid. , what might cause
“alarm” to a “resident of the premises,” ibid. , what is
“expected” of “ordinary visitors,” ibid. , and what would be
expected from a “ ‘reasonably respectful citizen,’ ” post, at 7. These are good questions. But their answers are
incompatible with the dissent’s outcome, which is presumably why
the dissent does not even try to argue that it would be customary,
usual, reasonable, respectful, ordinary, typical, nonalarming,
etc . , for a stranger to explore the curtilage of the home
with trained drug dogs. 3 The dissent insists that
our argument must rest upon “the particular instrument that
Detective Bartelt used to detect the odor of mari-juana”—the dog. Post, at 8. It is not the dog that is the problem, but the
behavior that here involved use of the dog. We think a typical
person would find it “ ‘a cause for great alarm’ ” (the
kind of reaction the dis-sent quite rightly relies upon to justify
its no-night-visits rule, post, at 5) to find a stranger
snooping about his front porch with or without a dog.
The dissent would let the police do whatever they want by way of
gathering evidence so long as they stay on the base-path, to use a
baseball analogy—so long as they “stick to the path that is
typically used to approach a front door, such as a paved walkway.” Ibid. From that vantage point they can presumably peer into
the house through binoculars with impunity. That is not the law, as
even the State con-cedes. See Tr. of Oral Arg. 6. 4 The dissent argues,
citing King , that “gathering evidence—even damning
evidence—is a lawful activity that falls within the scope of the
license to approach.” Post, at 7. That is a false
generalization. What King establishes is that it is not a
Fourth Amendment search to approach the home in order to speak with
the occupant, because all are invited to do that . The mere
“purpose of discovering information,” post , at 8, in the
course of engaging in that permitted conduct does not cause it to
violate the Fourth Amendment. But no one is impliedly invited to
enter the protected premises of the home in order to do nothing but
conduct a search. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–564

															_________________

															FLORIDA, PETITIONER v. JOELIS
JARDINES

															on writ of certiorari to the supreme court of
florida

															[March 26, 2013]

															Justice Kagan, with whom Justice Ginsburg and
Justice Sotomayor join, concurring.

															For me, a simple analogy clinches this case—and
does so on privacy as well as property grounds. A stranger comes to
the front door of your home carrying super-high-powered binoculars.
See ante , at 7, n. 3. He doesn’t knock or say hello.
Instead, he stands on the porch and uses the binoculars to peer
through your windows, into your home’s furthest corners. It doesn’t
take long (the binoculars are really very fine): In just a couple
of minutes, his uncommon behavior allows him to learn details of
your life you disclose to no one. Has your “visitor” trespassed on
your property, exceeding the license you have granted to members of
the public to, say, drop off the mail or distribute campaign
flyers? Yes, he has. And has he also invaded your “reasonable
expectation of privacy,” by nosing into intimacies you sensibly
thought protected from disclosure? Katz v. United
States , 389 U.S.
347 , 360 (1967) (Harlan, J., concurring). Yes, of course, he
has done that too.

															That case is this case in every way that
matters. Here, police officers came to Joelis Jardines’ door with a
super-sensitive instrument, which they deployed to detect things
inside that they could not perceive unassisted. The equip-ment they
used was animal, not mineral. But contra the dissent, see post , at 2 (opinion of Alito, J.) (noting the ubiquity of
dogs in American households), that is of no significance in
determining whether a search occurred. Detective Bartelt’s dog was
not your neighbor’s pet, come to your porch on a leisurely stroll.
As this Court discussed earlier this Term, drug-detection dogs are
highly trained tools of law enforcement, geared to respond in
distinctive ways to specific scents so as to convey clear and
reliable information to their human partners. See Florida v. Harris , 568 U. S. ___ (2013) (slip op. at 2–3, 7–8).
They are to the poodle down the street as high-powered binoculars
are to a piece of plain glass. Like the binoculars, a
drug-detection dog is a specialized device for discovering objects
not in plain view (or plain smell). And as in the hypothetical
above, that device was aimed here at a home—the most private and
inviolate (or so we expect) of all the places and things the Fourth
Amendment protects. Was this activity a trespass? Yes, as the Court
holds to-day. Was it also an invasion of privacy? Yes, that as
well.

															The Court today treats this case under a
property rubric; I write separately to note that I could just as
happily have decided it by looking to Jardines’ privacy interests.
A decision along those lines would have looked . . .
well, much like this one. It would have talked about “ ‘the
right of a man to retreat into his own home and there be free from
unreasonable governmental intrusion.’ ” Ante , at 4
(quoting Silverman v. United States , 365 U.S.
505 , 511 (1961)). It would have insisted on maintaining the
“practical value” of that right by preventing police officers from
standing in an adjacent space and “trawl[ing] for evidence with
impunity.” Ante , at 4. It would have explained that
“ ‘privacy expectations are most heightened’ ” in the
home and the surrounding area. Ante , at 4–5 (quoting California v. Ciraolo , 476 U.S.
207 , 213 (1986)). And it would have determined that police
officers invade those shared expectations when they use trained
canine assistants to reveal within the confines of a home what they
could not otherwise have found there. See ante , at 6–7, and
nn. 2–3.

															It is not surprising that in a case involving a
search of a home, property concepts and privacy concepts should so
align. The law of property “naturally enough influence[s]” our
“shared social expectations” of what places should be free from
governmental incursions. Georgia v. Randolph , 547 U.S.
103 , 111 (2006); see Rakas v. Illinois , 439 U.S.
128 , 143, n. 12 (1978). And so the sentiment “my home is my
own,” while originating in property law, now also denotes a common
understanding—extending even beyond that law’s formal
protections—about an especially private sphere. Jardines’ home was
his property; it was also his most intimate and familiar space. The
analysis proceeding from each of those facts, as today’s decision
reveals, runs mostly along the same path.

															I can think of only one divergence: If we had
decided this case on privacy grounds, we would have realized that Kyllo v. United States , 533 U.S.
27 (2001), already resolved it.[ 1 ] The Kyllo Court held that police officers
conducted a search when they used a thermal-imaging device to
detect heat emanating from a private home, even though they
committed no trespass. Highlighting our intention to draw both a
“firm” and a “bright” line at “the entrance to the house,” id. , at 40, we announced the following rule:

															“Where, as here, the Government uses a
device that is not in general public use, to explore details of the
home that would previously have been unknowable without physical
intrusion, the surveillance is a ‘search’ and is presumptively
unreasonable without a warrant.” Ibid. That “firm” and “bright” rule governs this case:
The police officers here conducted a search because they used a
“device . . . not in general public use” (a trained
drug-detection dog) to “explore details of the home” (the presence
of certain substances) that they would not otherwise have
discovered without entering the premises.

															And again, the dissent’s argument that the
device is just a dog cannot change the equation. As Kyllo made clear, the “sense-enhancing” tool at issue may be “crude” or
“sophisticated,” may be old or new (drug-detection dogs actually go
back not “12,000 years” or “centuries,” post , at 2, 8, 12,
but only a few decades), may be either smaller or bigger than a
breadbox; still, “at least where (as here)” the device is not “in
general public use,” training it on a home violates our “minimal
expectation of privacy”—an expectation “that exists , and
that is acknowledged to be reasonable .” 533 U. S., at
34, 36.[ 2 ] That does not mean
the device is off-limits, as the dissent implies, see post ,
at 11–12; it just means police officers cannot use it to examine a
home without a warrant or exigent circumstance. See Brigham
City v. Stuart , 547 U.S.
398 , 403–404 (2006) (describing exigencies allowing the
warrantless search of a home).

															With these further thoughts, suggesting that a
focus on Jardines’ privacy interests would make an “easy cas[e]
easy” twice over, ante , at 10, I join the Court’s opinion in
full. Notes 1 The dissent claims,
alternatively, that Illinois v. Caballes , 543 U.S.
405 , 409–410 (2005), controls this case (or nearly does). See post , at 9, 11. But Caballes concerned a
drug-detection dog’s sniff of an automobile during a traffic stop.
See also Florida v. Harris , 568 U. S. ___
(2013). And we have held, over and over again, that people’s
expectations of privacy are much lower in their cars than in their
homes. See, e.g., Arizona v. Gant , 556 U.S.
332 , 345 (2009); Wyoming v. Houghton , 526 U.S.
295 , 303 (1999); New York v. Class , 475 U.S.
106 , 115 (1986); Cardwell v. Lewis , 417 U.S.
583 , 590–591 (1974) (plurality opinion). 2 The dissent’s other
principal reason for concluding that no violation of privacy
occurred in this case—that police officers themselves might detect
an aroma wafting from a house—works no better. If officers can
smell drugs coming from a house, they can use that information; a
human sniff is not a search, we can all agree. But it does not
follow that a person loses his expectation of privacy in the many
scents within his home that (his own nose capably tells him) are
not usually detectible by humans standing outside. And indeed, Kyllo already decided as much. In response to an identical
argument from the dissent in that case, see 533 U. S., at 43
(Stevens, J., dissenting) (noting that humans can sometimes detect
“heat emanating from a building”), the Kyllo Court stated:
“The dissent’s comparison of the thermal imaging to various
circumstances in which outside observers might be able to perceive,
without technology, the heat of the home . . . is quite
irrelevant. The fact that equivalent information could sometimes be
obtained by other means does not make lawful the use of means that
violate the Fourth Amendment. . . . In any event,
[at the time in question,] no outside observer could have discerned
the relative heat of Kyllo’s home without thermal imaging.” Id., at 35, n. 2. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–564

															_________________

															FLORIDA, PETITIONER v. JOELIS
JARDINES

															on writ of certiorari to the supreme court of
florida

															[March 26, 2013]

															Justice Alito, with whom The Chief Justice,
Jus- tice Kennedy, and Justice Breyer join, dissenting.

															The Court’s decision in this important Fourth
Amendment case is based on a putative rule of trespass law that is
nowhere to be found in the annals of Anglo-American
jurisprudence.

															The law of trespass generally gives members of
the public a license to use a walkway to approach the front door of
a house and to remain there for a brief time. This license is not
limited to persons who intend to speak to an occupant or who
actually do so. (Mail carriers and persons delivering packages and
flyers are examples of individuals who may lawfully approach a
front door without intending to converse.) Nor is the license
restricted to categories of visitors whom an occupant of the
dwelling is likely to welcome; as the Court acknowledges, this
license applies even to “solicitors, hawkers and peddlers of all
kinds.” Ante , at 6 (internal quotation marks omitted). And
the license even extends to police officers who wish to gather
evidence against an occupant (by asking potentially incriminating
questions).

															According to the Court, however, the police
officer in this case, Detective Bartelt, committed a trespass
because he was accompanied during his otherwise lawful visit to the
front door of respondent’s house by his dog, Franky. Where is the
authority evidencing such a rule? Dogs have been domesticated for
about 12,000 years;[ 1 ] they
were ubiquitous in both this country and Britain at the time of the
adoption of the Fourth Amendment;[ 2 ] and their acute sense of smell has been used in law
enforcement for centuries.[ 3 ]
Yet the Court has been unable to find a single case—from the United
States or any other common-law nation—that supports the rule on
which its decision is based. Thus, trespass law provides no support
for the Court’s holding today.

															The Court’s decision is also inconsistent with
the reasonable-expectations-of-privacy test that the Court adopted
in Katz v. United States , 389
U.S. 347 (1967). A reasonable person understands that odors
emanating from a house may be detected from locations that are open
to the public, and a reasonable person will not count on the
strength of those odors remaining within the range that, while
detectible by a dog, cannot be smelled by a human.

															For these reasons, I would hold that no search
within the meaning of the Fourth Amendment took place in this case,
and I would reverse the decision below.

															I

															The opinion of the Court may leave a reader
with the mistaken impression that Detective Bartelt and Franky
remained on respondent’s property for a prolonged period of time
and conducted a far-flung exploration of the front yard. See ante , at 4 (“trawl for evidence with impunity”), 7
(“marching his bloodhound into the garden”). But that is not what
happened.

															Detective Bartelt and Franky approached the
front door via the driveway and a paved path—the route that any
visitor would customarily use[ 4 ]—and Franky was on the kind of leash that any dog owner
might employ.[ 5 ] As Franky
approached the door, he started to track an airborne odor. He held
his head high and began “bracketing” the area (pacing back and
forth) in order to determine the strongest source of the smell.
App. 95–96. Detective Bartelt knew “the minute [he] observed” this
behavior that Franky had detected drugs. Id. , at 95. Upon
locating the odor’s strongest source, Franky sat at the base of the
front door, and at this point, Detective Bartelt and Franky im-
mediately returned to their patrol car. Id. , at 98.

															A critical fact that the Court omits is that, as
respondent’s counsel explained at oral argument, this entire
process—walking down the driveway and front path to the front door,
waiting for Franky to find the strongest source of the odor, and
walking back to the car—took approximately a minute or two. Tr. of
Oral Arg. 57–58. Thus, the amount of time that Franky and the
detective remained at the front porch was even less. The Court also
fails to mention that, while Detective Bartelt apparently did not
personally smell the odor of marijuana coming from the house,
another officer who subsequently stood on the front porch,
Detective Pedraja, did notice that smell and was able to identify
it. App. 81.

															II

															The Court concludes that the conduct in this
case was a search because Detective Bartelt exceeded the boundaries
of the license to approach the house that is recognized by the law
of trespass, but the Court’s interpretation of the scope of that
license is unfounded.

															A

															It is said that members of the public may
lawfully proceed along a walkway leading to the front door of a
house because custom grants them a license to do so. Breard v. Alexandria , 341 U.S.
622 , 626 (1951); Lakin v. Ames , 64 Mass. 198, 220
(1852); J. Bishop, Commentaries on the Non-Contract Law §823, p.
378 (1889). This rule encompasses categories of visitors whom most
homeowners almost certainly wish to allow to approach their front
doors—friends, relatives, mail carriers, persons making deliveries.
But it also reaches categories of visitors who are less universally
welcome—“solicitors,” “hawkers,” “peddlers,” and the like. The law
might attempt to draw fine lines between categories of welcome and
unwelcome visitors, distinguishing, for example, between tolerable
and intolerable door-to-door peddlers (Girl Scouts selling cookies
versus adults selling aluminum siding) or be- tween police officers
on agreeable and disagreeable missions (gathering information about
a bothersome neighbor versus asking potentially incriminating
questions). But the law of trespass has not attempted such a
difficult taxonomy. See Desnick v. American Broadcasting
Cos., 44 F.3d 1345 , 1351 (CA7 1995) (“[C]onsent to an entry is often
given legal effect even though the entrant has intentions that if
known to the owner of the property would cause him for perfectly
understandable and generally ethical or at least lawful reasons to
revoke his consent”); cf. Skinner v. Ogallala Public
School Dist. , 262 Neb. 387, 402, 631 N.W.2d 510 , 525 (2001) (“[I]n order to determine if a
business invitation is implied, the inquiry is not a subjective
assessment of why the visitor chose to visit the premises in a
particular instance”); Crown Cork & Seal Co. v. Kane , 213 Md. 152, 159, 131 A.2d 470, 473–474 (1957) (noting
that “there are many cases in which an invitation has been implied
from circumstances, such as custom,” and that this test is
“objective in that it stresses custom and the appearance of things”
as opposed to “the undisclosed intention of the visitor”).

															Of course, this license has certain spatial and
temporal limits. A visitor must stick to the path that is typically
used to approach a front door, such as a paved walkway. A visitor
cannot traipse through the garden, meander into the backyard, or
take other circuitous detours that veer from the pathway that a
visitor would customarily use. See, e.g., Robinson v. Virginia , 47 Va. App. 533, 549–550, 625 S.E.2d 651, 659
(2006) (en banc); United States v. Wells , 648 F.3d
671, 679–680 (CA8 2011) (police exceeded scope of their implied
invitation when they bypassed the front door and proceeded directly
to the back yard); State v. Harris , 919 S.W.2d 619 , 624 (Tenn. Crim. App. 1995) (“Any substantial
and unreasonable departure from an area where the public is
impliedly invited exceeds the scope of the implied invitation
. . . ” (internal quotation marks and brackets omitted));
1 W. LaFave, Search and Seizure §2.3(c), p. 578 (2004) (hereinafter
LaFave); id ., §2.3(f), at 600–603 (“[W]hen the police come
on to private property to conduct an investigation or for some
other legitimate purpose and restrict their movements to places
visitors could be expected to go (e.g., walkways, drive- ways,
porches), observations made from such vantage points are not
covered by the Fourth Amendment” (footnotes omitted)).

															Nor, as a general matter, may a visitor come to
the front door in the middle of the night without an express
invitation. See State v. Cada , 129 Idaho 224, 233,
923 P.2d 469, 478 (App. 1996) (“Furtive intrusion late at night or
in the predawn hours is not conduct that is expected from ordinary
visitors. Indeed, if observed by a resident of the premises, it
could be a cause for great alarm”).

															Similarly, a visitor may not linger at the front
door for an extended period. See 9 So. 3d 1, 11 (Fla. App. 2008)
(case below) (Cope, J., concurring in part and dissenting in part)
(“[T]here is no such thing as squatter’s rights on a front porch. A
stranger may not plop down uninvited to spend the afternoon in the
front porch rocking chair, or throw down a sleeping bag to spend
the night, or lurk on the front porch, looking in the windows”).
The license is limited to the amount of time it would customarily
take to approach the door, pause long enough to see if someone is
home, and (if not expressly invited to stay longer), leave.

															As I understand the law of trespass and the
scope of the implied license, a visitor who adheres to these
limitations is not necessarily required to ring the doorbell, knock
on the door, or attempt to speak with an occupant. For example,
mail carriers, persons making deliveries, and in- dividuals
distributing flyers may leave the items they are carrying and
depart without making any attempt to converse. A pedestrian or
motorist looking for a particular address may walk up to a front
door in order to check a house number that is hard to see from the
sidewalk or road. A neighbor who knows that the residents are away
may approach the door to retrieve an accumulation of newspapers
that might signal to a potential burglar that the house is
unoccupied.

															As the majority acknowledges, this implied
license to approach the front door extends to the police. See ante, at 6. As we recognized in Kentucky v. King , 563 U. S. ___ (2011), police officers do not
engage in a search when they approach the front door of a residence
and seek to engage in what is termed a “knock and talk,” i.e. , knocking on the door and seeking to speak to an
occupant for the purpose of gathering evidence. See id. , at
___ (slip op., at 16) (“When law enforcement officers who are not
armed with a warrant knock on a door, they do no more than any
private citizen might do”). See also 1 LaFave §2.3(e), at 592 (“It
is not objectionable for an officer to come upon that part of the
property which has been opened to public common use” (internal
quotation marks omitted)). Even when the objective of a “knock and
talk” is to obtain evidence that will lead to the homeowner’s
arrest and prosecution, the license to approach still applies. In
other words, gathering evidence—even damning evidence—is a lawful
activity that falls within the scope of the license to approach.
And when officers walk up to the front door of a house, they are
permitted to see, hear, and smell whatever can be detected from a
lawful vantage point. California v. Ciraolo , 476 U.S.
207 , 213 (1986) (“The Fourth Amendment protection of the home
has never been extended to require law enforcement officers to
shield their eyes when passing by a home on public thoroughfares”); Cada , supra, at 232, 923 P. 2d, at 477
(“[P]olice officers restricting their activity to [areas to which
the public is impliedly invited] are permitted the same intrusion
and the same level of observation as would be expected from a
reasonably respectful citizen” (internal quotation marks omitted));
1 LaFave §§2.2(a), 2.3(c), at 450–452, 572–577.

															B

															Detective Bartelt did not exceed the scope of
the license to approach respondent’s front door. He adhered to the
customary path; he did not approach in the middle of the night; and
he remained at the front door for only a very short period (less
than a minute or two).

															The Court concludes that Detective Bartelt went
too far because he had the “ objectiv[e] . . . purpose to
conduct a search.” Ante , at 8 (emphasis added). What this
means, I take it, is that anyone aware of what Detective Bartelt
did would infer that his subjective purpose was to gather evidence.
But if this is the Court’s point, then a standard “knock and talk”
and most other police visits would likewise constitute searches.
With the exception of visits to serve warrants or civil process,
police almost always approach homes with a purpose of discovering
information. That is certainly the objective of a “knock and talk.”
The Court offers no meaningful way of distinguishing the “objective
purpose” of a “knock and talk” from the “objective purpose” of
Detective Bartelt’s conduct here.

															The Court contends that a “knock and talk” is
different because it involves talking, and “all are invited” to do
that. Ante , at 7–8, n. 4 (emphasis deleted). But a
police officer who approaches the front door of a house in
accordance with the limitations already discussed may gather
evidence by means other than talking. The officer may observe items
in plain view and smell odors coming from the house. Ciraolo , supra, at 213; Cada , 129
Idaho , at 232, 923 P. 2d, at 477; 1 LaFave §§2.2(a),
2.3(c), at 450–452, 572–577. So the Court’s “objective purpose”
argument cannot stand.

															What the Court must fall back on, then, is the
particular instrument that Detective Bartelt used to detect the
odor of marijuana, namely, his dog. But in the entire body of
common-law decisions, the Court has not found a single case holding
that a visitor to the front door of a home commits a trespass if
the visitor is accompanied by a dog on a leash. On the contrary,
the common law allowed even unleashed dogs to wander on private
property without committing a trespass. G. Williams, Liability for
Animals 136–146 (1939); J. Ingham, A Treatise on Property in
Animals Wild and Domestic and the Rights and Respon- sibilities
Arising Therefrom 277–278 (1900). Cf. B. Markesinis & S.
Deakin, Tort Law 511 (4th ed. 1999).

															The Court responds that “[i]t is not the dog
that is the problem, but the behavior that here involved use of the
dog.” Ante, at 7, n. 3. But where is the support in the law
of trespass for this proposition? Dogs’ keen sense of smell
has been used in law enforcement for centuries. The antiquity of
this practice is evidenced by a Scottish law from 1318 that made it
a crime to “disturb a tracking dog or the men coming with it for
pursuing thieves or seizing malefactors.” K. Brown et al., The
Records of the Parliaments of Scotland to 1707, (St Andrews,
2007–2013), online at http://www.rps.ac.uk/mss/1318/9. If bringing
a tracking dog to the front door of a home constituted a trespass,
one would expect at least one case to have arisen during the past
800 years. But the Court has found none.

															For these reasons, the real law of trespass
provides no support for the Court’s holding today. While the Court
claims that its reasoning has “ancient and durable roots,” ante, at 4, its trespass rule is really a newly struck
counterfeit.

															III

															The concurring opinion attempts to provide an
alternative ground for today’s decision, namely, that Detective
Bartelt’s conduct violated respondent’s reasonable expectations of
privacy. But we have already rejected a very similar, if not
identical argument, see Illinois v. Caballes , 543 U.S.
405 , 409–410 (2005), and in any event I see no basis for
concluding that the occupants of a dwelling have a reasonable
expectation of privacy in odors that emanate from the dwelling and
reach spots where members of the public may lawfully stand.

															It is clear that the occupant of a house has no
reasonable expectation of privacy with respect to odors that can be
smelled by human beings who are standing in such places. See United States v. Johns , 469 U.S.
478 , 482 (1985) (“After the officers came closer and detected
the distinct odor of marihuana, they had probable cause to believe
that the vehicles contained contraband”); United States v. Ventresca , 380 U.S.
102 , 111 (1965) (scent of ferment- ing mash supported probable
cause for warrant); United States v. Johnston , 497
F.2d 397, 398 (CA9 1974) (there is no “reasonable expectation of
privacy from drug agents with inquisitive nostrils”). And I would
not draw a line between odors that can be smelled by humans and
those that are detectible only by dogs.

															Consider the situation from the point of view of
the occupant of a building in which marijuana is grown or
methamphetamine is manufactured. Would such an oc- cupant reason as
follows? “I know that odors may emanate from my building and that
atmospheric conditions, such as the force and direction of the
wind, may affect the strength of those odors when they reach a spot
where members of the public may lawfully stand. I also know that
some people have a much more acute sense of smell than
others,[ 6 ] and I have no idea
who might be standing in one of the spots in question when the
odors from my house reach that location. In addition, I know that
odors coming from my building, when they reach these locations, may
be strong enough to be detected by a dog. But I am confident that
they will be so faint that they cannot be smelled by any human
being.” Such a finely tuned expectation would be entirely
unrealistic, and I see no evidence that society is prepared to
recognize it as reasonable.

															In an attempt to show that respondent had a
reasonable expectation of privacy in the odor of marijuana wafting
from his house, the concurrence argues that this case is just like Kyllo v. United States , 533 U.S.
27 (2001), which held that police officers conducted a search
when they used a thermal imaging device to detect heat emanating
from a house. Ante , at 3–4 (opinion of Kagan, J.). This
Court, however, has already rejected the argument that the use of a
drug-sniffing dog is the same as the use of a thermal imaging
device. See Caballes , 543 U. S., at 409–410. The very
argument now advanced by the concurrence appears in Justice
Souter’s Caballes dissent. See id ., at 413, and
n. 3. But the Court was not persuaded.

															Contrary to the interpretation propounded by the
concurrence, Kyllo is best understood as a decision about
the use of new technology. The Kyllo Court focused on the
fact that the thermal imaging device was a form of “sense-enhancing
technology” that was “not in general public use,” and it expressed
concern that citizens would be “at the mercy of advancing
technology” if its use was not restricted. 533 U. S., at
34–35. A dog, however, is not a new form of “technology or a
“device.” And, as noted, the use of dogs’ acute sense of smell in
law enforcement dates back many centuries.

															The concurrence suggests that a Kyllo -based decision would be “much like” the actual
decision of the Court, but that is simply not so. The holding of
the Court is based on what the Court sees as a “ ‘physical
intrusion of a constitutionally protected area.’ ” Ante , at 3 (quoting United States v. Knotts , 460 U.S.
276 , 286 (1983) (Brennan, J., concurring in judgment)). As a
result, it does not apply when a dog alerts while on a public
sidewalk or street or in the corridor of a building to which the
dog and handler have been lawfully admitted.

															The concurrence’s Kyllo -based approach
would have a much wider reach. When the police used the thermal
imaging device in Kyllo , they were on a public street, 533
U. S., at 29, and “committed no trespass.” Ante , at 3.
Therefore, if a dog’s nose is just like a thermal imaging device
for Fourth Amendment purposes, a search would occur if a dog
alerted while on a public sidewalk or in the corridor of an
apartment building. And the same would be true if the dog was
trained to sniff, not for marijuana, but for more dangerous quarry,
such as explosives or for a violent fugitive or kidnaped child. I
see no ground for hampering legitimate law enforcement in this
way.

															IV

															The conduct of the police officer in this case
did not constitute a trespass and did not violate respondent’s
reasonable expectations of privacy. I would hold that this conduct
was not a search, and I therefore respectfully dissent. Notes 1 See, e.g., Sloane,
Dogs in War, Police Work and on Patrol, 46 J. Crim. L., C. & P.
S. 385 (1955–1956) (hereinafter Sloane). 2 M. Derr, A Dog’s History
of America 68–92 (2004); K. Olsen, Daily Life in 18th-Century
England 32–33 (1999). 3 Sloane
388–389. 4 See App. 94; App. to
Brief for Respondent 1A (depiction of respondent’s
home). 5 The Court notes that
Franky was on a 6-foot leash, but such aleash is standard equipment
for ordinary dog owners. See, e.g., J. Stregowski, Four Dog
Leash Varieties,
http://dogs.about.com/od/toyssupplies/tp/Dog-Leashes.htm (all
Internet materials as visited Mar. 21, 2013, and available in Clerk
of Court’s case file). 6 Some humans naturally
have a much more acute sense of smell than others, and humans can
be trained to detect and distinguish odors that could not be
detected without such training. See E. Hancock, A Primer on Smell,
http://www.jhu.edu/jhumag/996web/smell.html. Some individuals
employed in the perfume and wine industries, for example, have an
amazingly acute sense of smell. Ibid.

Summary: The Supreme Court ruled that using a drug-sniffing dog on a homeowner's porch to investigate the contents of their home without a warrant is a violation of the Fourth Amendment. The Court considered the act a "search," and therefore unconstitutional.