Constitutional Law Cases: Rehnquist Court
2000
KYLLO v. UNITED STATES
certiorari to the united states court of appeals for the ninth circuit
No. 99-8508.
Argued February 20, 2001
Decided June 11, 2001
Suspicious that marijuana was being grown in petitioner Kyllo's home in a triplex,
agents used a thermal imaging device to scan the triplex to determine if the amount
of heat emanating from it was consistent with the high-intensity lamps typically used
for indoor marijuana growth. The scan showed that Kyllo's garage roof and a side wall
were relatively hot compared to the rest of his home and substantially warmer than
the neighboring units. Based in part on the thermal imaging, a Federal Magistrate
Judge issued a warrant to search Kyllo's home, where the agents found marijuana growing.
After Kyllo was indicted on a federal drug charge, he unsuccessfully moved to suppress
the evidence seized from his home and then entered a conditional guilty plea. The
Ninth Circuit ultimately affirmed, upholding the thermal imaging on the ground that
Kyllo had shown no subjective expectation of privacy because he had made no attempt
to conceal the heat escaping from his home. Even if he had, ruled the court, there
was no objectively reasonable expectation of privacy because the thermal imager did
not expose any intimate details of Kyllo's life, only amorphous hot spots on his home's
exterior.
Held: Where, as here, the Government uses a device that is not in general public
use, to explore details of a private home that would previously have been unknowable
without physical intrusion, the surveillance is a Fourth Amendment "search," and is
presumptively unreasonable without a warrant. Pp. 3-13.
(a) The question whether a warrantless search of a home is reasonable and hence constitutional
must be answered no in most instances, but the antecedent question whether a Fourth
Amendment "search" has occurred is not so simple. This Court has approved warrantless
visual surveillance of a home, see California v. Ciraolo, 476 U. S. 207, 213, ruling
that visual observation is no "search" at all, see Dow Chemical Co. v. United States,
476 U. S. 227, 234-235, 239. In assessing when a search is not a search, the Court
has adapted a principle first enunciated in Katz v. United States, 389 U. S. 347,
361: A "search" does not occur--even when its object is a house explicitly protected
by the Fourth Amendment--unless the individual manifested a subjective expectation
of privacy in the searched object, and society is willing to recognize that expectation
as reasonable, see, e.g., California v. Ciraolo, supra, at 211. Pp. 3-5.
(b) While it may be difficult to refine the Katz test in some instances, in the case
of the search of a home's interior--the prototypical and hence most commonly litigated
area of protected privacy--there is a ready criterion, with roots deep in the common
law, of the minimal expectation of privacy that exists, and that is acknowledged to
be reasonable. To withdraw protection of this minimum expectation would be to permit
police technology to erode the privacy guaranteed by the Fourth Amendment. Thus, obtaining
by sense-enhancing technology any information regarding the home's interior that could
not otherwise have been obtained without physical "intrusion into a constitutionally
protected area," Silverman v. United States, 365 U. S. 505, 512, constitutes a search--at
least where (as here) the technology in question is not in general public use. This
assures preservation of that degree of privacy against government that existed when
the Fourth Amendment was adopted. Pp. 6-7.
(c) Based on this criterion, the information obtained by the thermal imager in this
case was the product of a search. The Court rejects the Government's argument that
the thermal imaging must be upheld because it detected only heat radiating from the
home's external surface. Such a mechanical interpretation of the Fourth Amendment
was rejected in Katz, where the eavesdropping device in question picked up only sound
waves that reached the exterior of the phone booth to which it was attached. Reversing
that approach would leave the homeowner at the mercy of advancing technology--including
imaging technology that could discern all human activity in the home. Also rejected
is the Government's contention that the thermal imaging was constitutional because
it did not detect "intimate details." Such an approach would be wrong in principle
because, in the sanctity of the home, all details are intimate details. See e.g.,
United States v. Karo, 468 U. S. 705; Dow Chemical, supra, at 238, distinguished.
It would also be impractical in application, failing to provide a workable accommodation
between law enforcement needs and Fourth Amendment interests. See Oliver v. United
States, 466 U. S. 170, 181. Pp. 7-12.
(d) Since the imaging in this case was an unlawful search, it will remain for the
District Court to determine whether, without the evidence it provided, the search
warrant was supported by probable cause--and if not, whether there is any other basis
for supporting admission of that evidence. Pp. 12-13.
190 F. 3d 1041, reversed and remanded.
Scalia, J., delivered the opinion of the Court, in which Souter, Thomas, Ginsburg,
and Breyer, JJ., joined. Stevens, J., filed a dissenting opinion, in which Rehnquist,
C. J., and O'Connor and Kennedy, JJ., joined.
DANNY LEE KYLLO, PETITIONER v. UNITED STATES
on writ of certiorari to the united states court of appeals for the ninth circuit
[June 11, 2001]
Justice Scalia delivered the opinion of the Court.
This case presents the question whether the use of a thermal-imaging device aimed
at a private home from a public street to detect relative amounts of heat within the
home constitutes a "search" within the meaning of the Fourth Amendment.
I
In 1991 Agent William Elliott of the United States Department of the Interior came
to suspect that marijuana was being grown in the home belonging to petitioner Danny
Kyllo, part of a triplex on Rhododendron Drive in Florence, Oregon. Indoor marijuana
growth typically requires high-intensity lamps. In order to determine whether an amount
of heat was emanating from petitioner's home consistent with the use of such lamps,
at 3:20 a.m. on January 16, 1992, Agent Elliott and Dan Haas used an Agema Thermovision
210 thermal imager to scan the triplex. Thermal imagers detect infrared radiation,
which virtually all objects emit but which is not visible to the naked eye. The imager
converts radiation into images based on relative warmth--black is cool, white is hot,
shades of gray connote relative differences; in that respect, it operates somewhat
like a video camera showing heat images. The scan of Kyllo's home took only a few
minutes and was performed from the passenger seat of Agent Elliott's vehicle across
the street from the front of the house and also from the street in back of the house.
The scan showed that the roof over the garage and a side wall of petitioner's home
were relatively hot compared to the rest of the home and substantially warmer than
neighboring homes in the triplex. Agent Elliott concluded that petitioner was using
halide lights to grow marijuana in his house, which indeed he was. Based on tips from
informants, utility bills, and the thermal imaging, a Federal Magistrate Judge issued
a warrant authorizing a search of petitioner's home, and the agents found an indoor
growing operation involving more than 100 plants. Petitioner was indicted on one count
of manufacturing marijuana, in violation of 21 U. S. C. §841(a)(1). He unsuccessfully
moved to suppress the evidence seized from his home and then entered a conditional
guilty plea.
The Court of Appeals for the Ninth Circuit remanded the case for an evidentiary hearing
regarding the intrusiveness of thermal imaging. On remand the District Court found
that the Agema 210 "is a non-intrusive device which emits no rays or beams and shows
a crude visual image of the heat being radiated from the outside of the house"; it
"did not show any people or activity within the walls of the structure"; "[t]he device
used cannot penetrate walls or windows to reveal conversations or human activities";
and "[n]o intimate details of the home were observed." Supp. App. to Pet. for Cert.
39-40. Based on these findings, the District Court upheld the validity of the warrant
that relied in part upon the thermal imaging, and reaffirmed its denial of the motion
to suppress. A divided Court of Appeals initially reversed, 140 F. 3d 1249 (1998),
but that opinion was withdrawn and the panel (after a change in composition) affirmed,
190 F. 3d 1041 (1999), with Judge Noonan dissenting. The court held that petitioner
had shown no subjective expectation of privacy because he had made no attempt to conceal
the heat escaping from his home, id., at 1046, and even if he had, there was no objectively
reasonable expectation of privacy because the imager "did not expose any intimate
details of Kyllo's life," only "amorphous `hot spots' on the roof and exterior wall,"
id., at 1047. We granted certiorari. 530 U. S. 1305 (2000).
II
The Fourth Amendment provides that "[t]he right of the people to be secure in their
persons, houses, papers, and effects, against unreasonable searches and seizures,
shall not be violated." "At the very core" of the Fourth Amendment "stands the right
of a man to retreat into his own home and there be free from unreasonable governmental
intrusion." Silverman v. United States, 365 U. S. 505, 511 (1961). With few exceptions,
the question whether a warrantless search of a home is reasonable and hence constitutional
must be answered no. See Illinois v. Rodriguez, 497 U. S. 177, 181 (1990); Payton
v. New York, 445 U. S. 573, 586 (1980).
On the other hand, the antecedent question of whether or not a Fourth Amendment "search"
has occurred is not so simple under our precedent. The permissibility of ordinary
visual surveillance of a home used to be clear because, well into the 20th century,
our Fourth Amendment jurisprudence was tied to common-law trespass. See, e.g., Goldman
v. United States, 316 U. S. 129, 134-136 (1942); Olmstead v. United States, 277 U.
S. 438,
464-466 (1928). Cf. Silverman v. United States, supra, at 510-512 (technical trespass
not necessary for Fourth Amendment violation; it suffices if there is "actual intrusion
into a constitutionally protected area"). Visual surveillance was unquestionably lawful
because " `the eye cannot by the laws of England be guilty of a trespass.' " Boyd
v. United States, 116 U. S. 616, 628 (1886) (quoting Entick v. Carrington, 19 How.
St. Tr. 1029, 95 Eng. Rep. 807 (K. B. 1765)). We have since decoupled violation of
a person's Fourth Amendment rights from trespassory violation of his property, see
Rakas v. Illinois, 439 U. S. 128, 143 (1978), but the lawfulness of warrantless visual
surveillance of a home has still been preserved. As we observed in California v. Ciraolo,
476 U. S. 207, 213 (1986), "[t]he 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."
One might think that the new validating rationale would be that examining the portion
of a house that is in plain public view, while it is a "search"1 despite the absence
of trespass, is not an "unreasonable" one under the Fourth Amendment. See Minnesota
v. Carter, 525 U. S. 83, 104 (1998) (Breyer, J., concurring in judgment). But in fact
we have held that visual observation is no "search" at all--perhaps in order to preserve
somewhat more intact our doctrine that warrantless searches are presumptively unconstitutional.
See Dow Chemical Co. v. United States, 476 U. S. 227, 234-235, 239 (1986). In assessing
when a search is not a search, we have applied somewhat in reverse the principle first
enunciated in Katz v. United States, 389 U. S. 347 (1967). Katz involved eavesdropping
by means of an electronic listening device placed on the outside of a telephone booth--a
location not within the catalog ("persons, houses, papers, and effects") that the
Fourth Amendment protects against unreasonable searches. We held that the Fourth Amendment
nonetheless protected Katz from the warrantless eavesdropping because he "justifiably
relied" upon the privacy of the telephone booth. Id., at 353. As Justice Harlan's
oft-quoted concurrence described it, a Fourth Amendment search occurs when the government
violates a subjective expectation of privacy that society recognizes as reasonable.
See id., at 361. We have subsequently applied this principle to hold that a Fourth
Amendment search does not occur--even when the explicitly protected location of a
house is concerned--unless "the individual manifested a subjective expectation of
privacy in the object of the challenged search," and "society [is] willing to recognize
that expectation as reasonable." Ciraolo, supra, at 211. We have applied this test
in holding that it is not a search for the police to use a pen register at the phone
company to determine what numbers were dialed in a private home, Smith v. Maryland,
442 U. S. 735, 743-744 (1979), and we have applied the test on two different occasions
in holding that aerial surveillance of private homes and surrounding areas does not
constitute a search, Ciraolo, supra; Florida v. Riley, 488 U. S. 445 (1989).
The present case involves officers on a public street engaged in more than naked-eye
surveillance of a home. We have previously reserved judgment as to how much technological
enhancement of ordinary perception from such a vantage point, if any, is too much.
While we upheld enhanced aerial photography of an industrial complex in Dow Chemical,
we noted that we found "it important that this is not an area immediately adjacent
to a private home, where privacy expectations are most heightened," 476 U. S., at
237, n. 4 (emphasis in original).
III
It would be foolish to contend that the degree of privacy secured to citizens by
the Fourth Amendment has been entirely unaffected by the advance of technology. For
example, as the cases discussed above make clear, the technology enabling human flight
has exposed to public view (and hence, we have said, to official observation) uncovered
portions of the house and its curtilage that once were private. See Ciraolo, supra,
at 215. The question we confront today is what limits there are upon this power of
technology to shrink the realm of guaranteed privacy.
The Katz test--whether the individual has an expectation of privacy that society
is prepared to recognize as reasonable--has often been criticized as circular, and
hence subjective and unpredictable. See 1 W. LaFave, Search and Seizure §2.1(d), pp.
393-394 (3d ed. 1996); Posner, The Uncertain Protection of Privacy by the Supreme
Court, 1979 S. Ct. Rev. 173, 188; Carter, supra, at 97 (Scalia, J., concurring). But
see Rakas, supra, at 143-144, n. 12. While it may be difficult to refine Katz when
the search of areas such as telephone booths, automobiles, or even the curtilage and
uncovered portions of residences are at issue, in the case of the search of the interior
of homes--the prototypical and hence most commonly litigated area of protected privacy--there
is a ready criterion, with roots deep in the common law, of the minimal expectation
of privacy that exists, and that is acknowledged to be reasonable. To withdraw protection
of this minimum expectation would be to permit police technology to erode the privacy
guaranteed by the Fourth Amendment. We think that obtaining by sense-enhancing technology
any information regarding the interior of the home that could not otherwise have been
obtained without physical "intrusion into a constitutionally protected area," Silverman,
365 U. S., at 512, constitutes a search--at least where (as here) the technology in
question is not in general public use. This assures preservation of that degree of
privacy against government that existed when the Fourth Amendment was adopted. On
the basis of this criterion, the information obtained by the thermal imager in this
case was the product of a search.2
The Government maintains, however, that the thermal imaging must be upheld because
it detected "only heat radiating from the external surface of the house," Brief for
United States 26. The dissent makes this its leading point, see post, at 1, contending
that there is a fundamental difference between what it calls "off-the-wall" observations
and "through-the-wall surveillance." But just as a thermal imager captures only heat
emanating from a house, so also a powerful directional microphone picks up only sound
emanating from a house-and a satellite capable of scanning from many miles away would
pick up only visible light emanating from a house. We rejected such a mechanical interpretation
of the Fourth Amendment in Katz, where the eavesdropping device picked up only sound
waves that reached the exterior of the phone booth. Reversing that approach would
leave the homeowner at the mercy of advancing technology--including imaging technology
that could discern all human activity in the home. While the technology used in the
present case was relatively crude, the rule we adopt must take account of more sophisticated
systems that are already in use or in development.3 The dissent's reliance on the
distinction between "off-the-wall" and "through-the-wall" observation is entirely
incompatible with the dissent's belief, which we discuss below, that thermal-imaging
observations of the intimate details of a home are impermissible. The most sophisticated
thermal imaging devices continue to measure heat "off-the-wall" rather than "through-the-wall";
the dissent's disapproval of those more sophisticated thermal-imaging devices, see
post, at 10, is an acknowledgement that there is no substance to this distinction.
As for the dissent's extraordinary assertion that anything learned through "an inference"
cannot be a search, see post, at 4-5, that would validate even the "through-the-wall"
technologies that the dissent purports to disapprove. Surely the dissent does not
believe that the through-the-wall radar or ultrasound technology produces an 8-by-10
Kodak glossy that needs no analysis (i.e., the making of inferences). And, of course,
the novel proposition that inference insulates a search is blatantly contrary to United
States v. Karo, 468 U. S. 705 (1984), where the police "inferred" from the activation
of a beeper that a certain can of ether was in the home. The police activity was held
to be a search, and the search was held unlawful.4
The Government also contends that the thermal imaging was constitutional because
it did not "detect private activities occurring in private areas," Brief for United
States 22. It points out that in Dow Chemical we observed that the enhanced aerial
photography did not reveal any "intimate details." 476 U. S., at 238. Dow Chemical,
however, involved enhanced aerial photography of an industrial complex, which does
not share the Fourth Amendment sanctity of the home. The Fourth Amendment's protection
of the home has never been tied to measurement of the quality or quantity of information
obtained. In Silverman, for example, we made clear that any physical invasion of the
structure of the home, "by even a fraction of an inch," was too much, 365 U. S., at
512, and there is certainly no exception to the warrant requirement for the officer
who barely cracks open the front door and sees nothing but the nonintimate rug on
the vestibule floor. In the home, our cases show, all details are intimate details,
because the entire area is held safe from prying government eyes. Thus, in Karo, supra,
the only thing detected was a can of ether in the home; and in Arizona v. Hicks, 480
U. S. 321 (1987), the only thing detected by a physical search that went beyond what
officers lawfully present could observe in "plain view" was the registration number
of a phonograph turntable. These were intimate details because they were details of
the home, just as was the detail of how warm--or even how relatively warm--Kyllo was
heating his residence.5
Limiting the prohibition of thermal imaging to "intimate details" would not only
be wrong in principle; it would be impractical in application, failing to provide
"a workable accommodation between the needs of law enforcement and the interests protected
by the Fourth Amendment," Oliver v. United States, 466 U. S. 170, 181 (1984). To begin
with, there is no necessary connection between the sophistication of the surveillance
equipment and the "intimacy" of the details that it observes--which means that one
cannot say (and the police cannot be assured) that use of the relatively crude equipment
at issue here will always be lawful. The Agema Thermovision 210 might disclose, for
example, at what hour each night the lady of the house takes her daily sauna and bath--a
detail that many would consider "intimate"; and a much more sophisticated system might
detect nothing more intimate than the fact that someone left a closet light on. We
could not, in other words, develop a rule approving only that through-the-wall surveillance
which identifies objects no smaller than 36 by 36 inches, but would have to develop
a jurisprudence specifying which home activities are "intimate" and which are not.
And even when (if ever) that jurisprudence were fully developed, no police officer
would be able to know in advance whether his through-the-wall surveillance picks up
"intimate" details--and thus would be unable to know in advance whether it is constitutional.
The dissent's proposed standard--whether the technology offers the "functional equivalent
of actual presence in the area being searched," post, at 7--would seem quite similar
to our own at first blush. The dissent concludes that Katz was such a case, but then
inexplicably asserts that if the same listening device only revealed the volume of
the conversation, the surveillance would be permissible, post, at 10. Yet if, without
technology, the police could not discern volume without being actually present in
the phone booth, Justice Stevens should conclude a search has occurred. Cf. Karo,
supra, at 735 (Stevens, J., concurring in part and dissenting in part) ("I find little
comfort in the Court's notion that no invasion of privacy occurs until a listener
obtains some significant information by use of the device... . A bathtub is a less
private area when the plumber is present even if his back is turned"). The same should
hold for the interior heat of the home if only a person present in the home could
discern the heat. Thus the driving force of the dissent, despite its recitation of
the above standard, appears to be a distinction among different types of information--whether
the "homeowner would even care if anybody noticed," post, at 10. The dissent offers
no practical guidance for the application of this standard, and for reasons already
discussed, we believe there can be none. The people in their houses, as well as the
police, deserve more precision.6
We have said that the Fourth Amendment draws "a firm line at the entrance to the
house," Payton, 445 U. S., at 590. That line, we think, must be not only firm but
also bright--which requires clear specification of those methods of surveillance that
require a warrant. While it is certainly possible to conclude from the videotape of
the thermal imaging that occurred in this case that no "significant" compromise of
the homeowner's privacy has occurred, we must take the long view, from the original
meaning of the Fourth Amendment forward.
"The Fourth Amendment is to be construed in the light of what was deemed an unreasonable
search and seizure when it was adopted, and in a manner which will conserve public
interests as well as the interests and rights of individual citizens." Carroll v.
United States, 267 U. S. 132, 149 (1925).
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.
Since we hold the Thermovision imaging to have been an unlawful search, it will remain
for the District Court to determine whether, without the evidence it provided, the
search warrant issued in this case was supported by probable cause--and if not, whether
there is any other basis for supporting admission of the evidence that the search
pursuant to the warrant produced.
* * *
The judgment of the Court of Appeals is reversed; the case is remanded for further
proceedings consistent with this opinion.
It is so ordered.
DANNY LEE KYLLO, PETITIONER v. UNITED STATES
on writ of certiorari to the united states court of appeals for the ninth circuit
[June 11, 2001]
Justice Stevens, with whom The Chief Justice, Justice O'Connor, and Justice Kennedy
join,
dissenting.
There is, in my judgment, a distinction of constitutional magnitude between "through-the-wall
surveillance" that gives the observer or listener direct access to information in
a private area, on the one hand, and the thought processes used to draw inferences
from information in the public domain, on the other hand. The Court has crafted a
rule that purports to deal with direct observations of the inside of the home, but
the case before us merely involves indirect deductions from "off-the-wall" surveillance,
that is, observations of the exterior of the home. Those observations were made with
a fairly primitive thermal imager that gathered data exposed on the outside of petitioner's
home but did not invade any constitutionally protected interest in privacy.1 Moreover,
I believe that the supposedly "bright-line" rule the Court has created in response
to its concerns about future technological developments is unnecessary, unwise, and
inconsistent with the Fourth Amendment.
I
There is no need for the Court to craft a new rule to decide this case, as it is
controlled by established principles from our Fourth Amendment jurisprudence. One
of those core principles, of course, is that "searches and seizures inside a home
without a warrant are presumptively unreasonable." Payton v. New York, 445 U. S. 573,
586 (1980) (emphasis added). But it is equally well settled that searches and seizures
of property in plain view are presumptively reasonable. See id., at 586-587.2 Whether
that property is residential or commercial, the basic principle is the same: " `What
a person knowingly exposes to the public, even in his own home or office, is not a
subject of Fourth Amendment protection.' " California v. Ciraolo, 476 U. S. 207, 213
(1986) (quoting Katz v. United States, 389 U. S. 347, 351 (1967)); see Florida v.
Riley, 488 U. S. 445, 449-450 (1989); California v. Greenwood, 486 U. S. 35, 40-41
(1988); Dow Chemical Co. v. United States, 476 U. S. 227, 235-236 (1986); Air Pollution
Variance Bd. of Colo. v. Western Alfalfa Corp., 416 U. S. 861, 865 (1974). That is
the principle implicated here.
While the Court "take[s] the long view" and decides this case based largely on the
potential of yet-to-be-developed technology that might allow "through-the-wall surveillance,"
ante, at 11-12; see ante, at 8, n. 3, this case involves nothing more than off-the-wall
surveillance by law enforcement officers to gather information exposed to the general
public from the outside of petitioner's home. All that the infrared camera did in
this case was passively measure heat emitted from the exterior surfaces of petitioner's
home; all that those measurements showed were relative differences in emission levels,
vaguely indicating that some areas of the roof and outside walls were warmer than
others. As still images from the infrared scans show, see Appendix, infra, no details
regarding the interior of petitioner's home were revealed. Unlike an x-ray scan, or
other possible "through-the-wall" techniques, the detection of infrared radiation
emanating from the home did not accomplish "an unauthorized physical penetration into
the premises," Silverman v. United States, 365 U. S. 505, 509 (1961), nor did it "obtain
information that it could not have obtained by observation from outside the curtilage
of the house," United States v. Karo, 468 U. S. 705, 715 (1984).
Indeed, the ordinary use of the senses might enable a neighbor or passerby to notice
the heat emanating from a building, particularly if it is vented, as was the case
here. Additionally, any member of the public might notice that one part of a house
is warmer than another part or a nearby building if, for example, rainwater evaporates
or snow melts at different rates across its surfaces. Such use of the senses would
not convert into an unreasonable search if, instead, an adjoining neighbor allowed
an officer onto her property to verify her perceptions with a sensitive thermometer.
Nor, in my view, does such observation become an unreasonable search if made from
a distance with the aid of a device that merely discloses that the exterior of one
house, or one area of the house, is much warmer than another. Nothing more occurred
in this case.
Thus, the notion that heat emissions from the outside of a dwelling is a private
matter implicating the protections of the Fourth Amendment (the text of which guarantees
the right of people "to be secure in their ... houses" against unreasonable searches
and seizures (emphasis added)) is not only unprecedented but also quite difficult
to take seriously. Heat waves, like aromas that are generated in a kitchen, or in
a laboratory or opium den, enter the public domain if and when they leave a building.
A subjective expectation that they would remain private is not only implausible but
also surely not "one that society is prepared to recognize as `reasonable.' " Katz,
389 U. S., at 361 (Harlan, J., concurring).
To be sure, the homeowner has a reasonable expectation of privacy concerning what
takes place within the home, and the Fourth Amendment's protection against physical
invasions of the home should apply to their functional equivalent. But the equipment
in this case did not penetrate the walls of petitioner's home, and while it did pick
up "details of the home" that were exposed to the public, ante, at 10, it did not
obtain "any information regarding the interior of the home," ante, at 6 (emphasis
added). In the Court's own words, based on what the thermal imager "showed" regarding
the outside of petitioner's home, the officers "concluded" that petitioner was engaging
in illegal activity inside the home. Ante, at 2. It would be quite absurd to characterize
their thought processes as "searches," regardless of whether they inferred (rightly)
that petitioner was growing marijuana in his house, or (wrongly) that "the lady of
the house [was taking] her daily sauna and bath." Ante, at 10-11. In either case,
the only conclusions the officers reached concerning the interior of the home were
at least as indirect as those that might have been inferred from the contents of discarded
garbage, see California v. Greenwood, 486 U. S. 35 (1988), or pen register data, see
Smith v. Maryland, 442 U. S. 735 (1979), or, as in this case, subpoenaed utility records,
see 190 F. 3d 1041, 1043 (CA9 1999). For the first time in its history, the Court
assumes that an inference can amount to a Fourth Amendment violation. See ante, at
8.3
Notwithstanding the implications of today's decision, there is a strong public interest
in avoiding constitutional litigation over the monitoring of emissions from homes,
and over the inferences drawn from such monitoring. Just as "the police cannot reasonably
be expected to avert their eyes from evidence of criminal activity that could have
been observed by any member of the public," Greenwood, 486 U. S., at 41, so too public
officials should not have to avert their senses or their equipment from detecting
emissions in the public domain such as excessive heat, traces of smoke, suspicious
odors, odorless gases, airborne particulates, or radioactive emissions, any of which
could identify hazards to the community. In my judgment, monitoring such emissions
with "sense-enhancing technology," ante, at 6, and drawing useful conclusions from
such monitoring, is an entirely reasonable public service.
On the other hand, the countervailing privacy interest is at best trivial. After
all, homes generally are insulated to keep heat in, rather than to prevent the detection
of heat going out, and it does not seem to me that society will suffer from a rule
requiring the rare homeowner who both intends to engage in uncommon activities that
produce extraordinary amounts of heat, and wishes to conceal that production from
outsiders, to make sure that the surrounding area is well insulated. Cf. United States
v. Jacobsen, 466 U. S. 109, 122 (1984) ("The concept of an interest in privacy that
society is prepared to recognize as reasonable is, by its very nature, critically
different from the mere expectation, however well justified, that certain facts will
not come to the attention of the authorities"). The interest in concealing the heat
escaping from one's house pales in significance to the "the chief evil against which
the wording of the Fourth Amendment is directed," the "physical entry of the home,"
United States v. United States Dist. Court for Eastern Dist. of Mich., 407 U. S. 297,
313 (1972), and it is hard to believe that it is an interest the Framers sought to
protect in our Constitution.
Since what was involved in this case was nothing more than drawing inferences from
off-the-wall surveillance, rather than any "through-the-wall" surveillance, the officers'
conduct did not amount to a search and was perfectly reasonable.4
II
Instead of trying to answer the question whether the use of the thermal imager in
this case was even arguably unreasonable, the Court has fashioned a rule that is intended
to provide essential guidance for the day when "more sophisticated systems" gain the
"ability to `see' through walls and other opaque barriers." Ante, at 8, and n. 3.
The newly minted rule encompasses "obtaining [1] by sense-enhancing technology [2]
any information regarding the interior of the home [3] that could not otherwise have
been obtained without physical intrusion into a constitutionally protected area ...
[4] at least where (as here) the technology in question is not in general public use."
Ante, at 6-7 (internal quotation marks omitted). In my judgment, the Court's new rule
is at once too broad and too narrow, and is not justified by the Court's explanation
for its adoption. As I have suggested, I would not erect a constitutional impediment
to the use of sense-enhancing technology unless it provides its user with the functional
equivalent of actual presence in the area being searched.
Despite the Court's attempt to draw a line that is "not only firm but also bright,"
ante, at 12, the contours of its new rule are uncertain because its protection apparently
dissipates as soon as the relevant technology is "in general public use," ante, at
6-7. Yet how much use is general public use is not even hinted at by the Court's opinion,
which makes the somewhat doubtful assumption that the thermal imager used in this
case does not satisfy that criterion.5 In any event, putting aside its lack of clarity,
this criterion is somewhat perverse because it seems likely that the threat to privacy
will grow, rather than recede, as the use of intrusive equipment becomes more readily
available.
It is clear, however, that the category of "sense-enhancing technology" covered by
the new rule, ante, at 6, is far too broad. It would, for example, embrace potential
mechanical substitutes for dogs trained to react when they sniff narcotics. But in
United States v. Place, 462 U. S. 696, 707 (1983), we held that a dog sniff that "discloses
only the presence or absence of narcotics" does "not constitute a `search' within
the meaning of the Fourth Amendment," and it must follow that sense-enhancing equipment
that identifies nothing but illegal activity is not a search either. Nevertheless,
the use of such a device would be unconstitutional under the Court's rule, as would
the use of other new devices that might detect the odor of deadly bacteria or chemicals
for making a new type of high explosive, even if the devices (like the dog sniffs)
are "so limited in both the manner in which" they obtain information and "in the content
of the information" they reveal. Ibid. If nothing more than that sort of information
could be obtained by using the devices in a public place to monitor emissions from
a house, then their use would be no more objectionable than the use of the thermal
imager in this case.
The application of the Court's new rule to "any information regarding the interior
of the home," ante, at 6, is also unnecessarily broad. If it takes sensitive equipment
to detect an odor that identifies criminal conduct and nothing else, the fact that
the odor emanates from the interior of a home should not provide it with constitutional
protection. See supra, at 7-8. The criterion, moreover, is too sweeping in that information
"regarding" the interior of a home apparently is not just information obtained through
its walls, but also information concerning the outside of the building that could
lead to (however many) inferences "regarding" what might be inside. Under that expansive
view, I suppose, an officer using an infrared camera to observe a man silently entering
the side door of a house at night carrying a pizza might conclude that its interior
is now occupied by someone who likes pizza, and by doing so the officer would be guilty
of conducting an unconstitutional "search" of the home.
Because the new rule applies to information regarding the "interior" of the home,
it is too narrow as well as too broad. Clearly, a rule that is designed to protect
individuals from the overly intrusive use of sense-enhancing equipment should not
be limited to a home. If such equipment did provide its user with the functional equivalent
of access to a private place--such as, for example, the telephone booth involved in
Katz, or an office building--then the rule should apply to such an area as well as
to a home. See Katz, 389 U. S., at 351 ("[T]he Fourth Amendment protects people, not
places").
The final requirement of the Court's new rule, that the information "could not otherwise
have been obtained without physical intrusion into a constitutionally protected area,"
ante, at 6 (internal quotation marks omitted), also extends too far as the Court applies
it. As noted, the Court effectively treats the mental process of analyzing data obtained
from external sources as the equivalent of a physical intrusion into the home. See
supra, at 4-5. As I have explained, however, the process of drawing inferences from
data in the public domain should not be characterized as a search.
The two reasons advanced by the Court as justifications for the adoption of its new
rule are both unpersuasive. First, the Court suggests that its rule is compelled by
our holding in Katz, because in that case, as in this, the surveillance consisted
of nothing more than the monitoring of waves emanating from a private area into the
public domain. See ante, at 7-8. Yet there are critical differences between the cases.
In Katz, the electronic listening device attached to the outside of the phone booth
allowed the officers to pick up the content of the conversation inside the booth,
making them the functional equivalent of intruders because they gathered information
that was otherwise available only to someone inside the private area; it would be
as if, in this case, the thermal imager presented a view of the heat-generating activity
inside petitioner's home. By contrast, the thermal imager here disclosed only the
relative amounts of heat radiating from the house; it would be as if, in Katz, the
listening device disclosed only the relative volume of sound leaving the booth, which
presumably was discernible in the public domain.6 Surely, there is a significant difference
between the general and well-settled expectation that strangers will not have direct
access to the contents of private communications, on the one hand, and the rather
theoretical expectation that an occasional homeowner would even care if anybody noticed
the relative amounts of heat emanating from the walls of his house, on the other.
It is pure hyperbole for the Court to suggest that refusing to extend the holding
of Katz to this case would leave the homeowner at the mercy of "technology that could
discern all human activity in the home." Ante, at 8.
Second, the Court argues that the permissibility of "through-the-wall surveillance"
cannot depend on a distinction between observing "intimate details" such as "the lady
of the house [taking] her daily sauna and bath," and noticing only "the nonintimate
rug on the vestibule floor" or "objects no smaller than 36 by 36 inches." Ante, at
10-11. This entire argument assumes, of course, that the thermal imager in this case
could or did perform "through-the-wall surveillance" that could identify any detail
"that would previously have been unknowable without physical intrusion." Ante, at
11-12. In fact, the device could not, see n. 1, supra, and did not, see Appendix,
infra, enable its user to identify either the lady of the house, the rug on the vestibule
floor, or anything else inside the house, whether smaller or larger than 36 by 36
inches. Indeed, the vague thermal images of petitioner's home that are reproduced
in the Appendix were submitted by him to the District Court as part of an expert report
raising the question whether the device could even take "accurate, consistent infrared
images" of the outside of his house. Defendant's Exhibit 107, p. 4. But even if the
device could reliably show extraordinary differences in the amounts of heat leaving
his home, drawing the inference that there was something suspicious occurring inside
the residence--a conclusion that officers far less gifted than Sherlock Holmes would
readily draw--does not qualify as "through-the-wall surveillance," much less a Fourth
Amendment violation.
III
Although the Court is properly and commendably concerned about the threats to privacy
that may flow from advances in the technology available to the law enforcement profession,
it has unfortunately failed to heed the tried and true counsel of judicial restraint.
Instead of concentrating on the rather mundane issue that is actually presented by
the case before it, the Court has endeavored to craft an all-encompassing rule for
the future. It would be far wiser to give legislators an unimpeded opportunity to
grapple with these emerging issues rather than
to shackle them with prematurely devised constitutional constraints.
I respectfully dissent.
APPENDIX
(Images and text reproduced from defendant's exhibit 107)
Top left: Infrared image of a video frame from the videotape submitted as evidence
in this case. The thermogram indicates the suspect house as it appeared with the Gain
and contrast in its default setting. Only the outline of the house is visible. The
camera used was the Thermovision 210.
Top Right: Infrared image of a subsequent videoframe taken from the videotape. The
gain and contrast settings have been increased in order to make the walls and roof
of the structure appear hotter than what it actually is.
[Graphic Image omitted; see printed opinion.]
Bottom Left: Infrared image of the opposite side of the suspects house. The thermogram
is also taken from the same videotape. The camera settings are in the default mode
and the outline of the house is barely visible. Only the hot electrical transformer
and the street light are identifiable.
Bottom Right: The same image, but with the gain and contrast increased. This change
in camera settings cause any object to appear hotter than what it actually is. The
arrow indicates the overloading of a area immediately around a hot object in this
case the electrical transformer and the streetlight. This overloading of the image
is a inherent design flaw in the camera itself.
FOOTNOTES
Footnote 1
When the Fourth Amendment was adopted, as now, to "search" meant "[t]o look over
or through for the purpose of finding something; to explore; to examine by inspection;
as, to search the house for a book; to search the wood for a thief." N. Webster, An
American Dictionary of the English Language 66 (1828) (reprint 6th ed. 1989).
Footnote 2
The dissent's repeated assertion that the thermal imaging did not obtain information
regarding the interior of the home, post, at 3, 4 (opinion of Stevens, J.), is simply
inaccurate. A thermal imager reveals the relative heat of various rooms in the home.
The dissent may not find that information particularly private or important, see post,
at 4, 5, 10, but there is no basis for saying it is not information regarding the
interior of the home. 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--for example, by observing snowmelt on the roof, post, at 3--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. The
police might, for example, learn how many people are in a particular house by setting
up year-round surveillance; but that does not make breaking and entering to find out
the same information lawful. In any event, on the night of January 16, 1992, no outside
observer could have discerned the relative heat of Kyllo's home without thermal imaging.
Footnote 3
The ability to "see" through walls and other opaque barriers is a clear, and scientifically
feasible, goal of law enforcement research and development. The National Law Enforcement
and Corrections Technology Center, a program within the United States Department of
Justice, features on its Internet Website projects that include a "Radar-Based Through-the-Wall
Surveillance System," "Handheld Ultrasound Through the Wall Surveillance," and a "Radar
Flashlight" that "will enable law officers to detect individuals through interior
building walls." www.nlectc.org/techproj/ (visited May 3, 2001). Some devices may
emit low levels of radiation that travel "through-the-wall," but others, such as more
sophisticated thermal imaging devices, are entirely passive, or "off-the-wall" as
the dissent puts it.
Footnote 4
The dissent asserts, post, at 5, n. 3, that we have misunderstood its point, which
is not that inference insulates a search, but that inference alone is not a search.
If we misunderstood the point, it was only in a good-faith effort to render the point
germane to the case at hand. The issue in this case is not the police's allegedly
unlawful inferencing, but their allegedly unlawful thermal-imaging measurement of
the emanations from a house. We say such measurement is a search; the dissent says
it is not, because an inference is not a search. We took that to mean that, since
the technologically enhanced emanations had to be the basis of inferences before anything
inside the house could be known, the use of the emanations could not be a search.
But the dissent certainly knows better than we what it intends. And if it means only
that an inference is not a search, we certainly agree. That has no bearing, however,
upon whether hi-tech measurement of emanations from a house is a search.
Footnote 5
The Government cites our statement in California v. Ciraolo, 476 U. S. 207 (1986),
noting apparent agreement with the State of California that aerial surveillance of
a house's curtilage could become " `invasive' " if " `modern technology' " revealed
" `those intimate associations, objects or activities otherwise imperceptible to police
or fellow citizens.' " Id., at 215, n. 3 (quoting brief of the State of California).
We think the Court's focus in this second-hand dictum was not upon intimacy but upon
otherwise-imperceptibility, which is precisely the principle we vindicate today.
Footnote 6
The dissent argues that we have injected potential uncertainty into the constitutional
analysis by noting that whether or not the technology is in general public use may
be a factor. See post, at 7-8. That quarrel, however, is not with us but with this
Court's precedent. See Ciraolo, supra, at 215 ("In an age where private and commercial
flight in the public airways is routine, it is unreasonable for respondent to expect
that his marijuana plants were constitutionally protected from being observed with
the naked eye from an altitude of 1,000 feet"). Given that we can quite confidently
say that thermal imaging is not "routine," we decline in this case to reexamine that
factor.
FOOTNOTES
Footnote 1
After an evidentiary hearing, the District Court found:
"[T]he use of the thermal imaging device here was not an intrusion into Kyllo's home.
No intimate details of the home were observed, and there was no intrusion upon the
privacy of the individuals within the home. The device used cannot penetrate walls
or windows to reveal conversations or human activities. The device recorded only the
heat being emitted from the home." Supp. App. to Pet. for Cert. 40.
Footnote 2
Thus, for example, we have found consistent with the Fourth Amendment, even absent
a warrant, the search and seizure of garbage left for collection outside the curtilage
of a home, California v. Greenwood, 486 U. S. 35 (1988); the aerial surveillance of
a fenced-in backyard from an altitude of 1,000 feet, California v. Ciraolo, 476 U.
S. 207 (1986); the aerial observation of a partially exposed interior of a residential
greenhouse from 400 feet above, Florida v. Riley, 488 U. S. 445 (1989); the aerial
photography of an industrial complex from several thousand feet above, Dow Chemical
Co. v. United States, 476 U. S. 227 (1986); and the observation of smoke emanating
from chimney stacks, Air Pollution Variance Bd. of Colo. v. Western Alfalfa Corp.,
416 U. S. 861 (1974).
Footnote 3
Although the Court credits us with the "novel proposition that inference insulates
a search," ante, at 9, our point simply is that an inference cannot be a search, contrary
to the Court's reasoning. See supra, at 4-5. Thus, the Court's use of United States
v. Karo, 468 U. S. 705 (1984), to refute a point we do not make underscores the fact
that the Court has no real answer (either in logic or in law) to the point we do make.
Of course, Karo itself does not provide any support for the Court's view that inferences
can amount to unconstitutional searches. The illegality in that case was "the monitoring
of a beeper in a private residence" to obtain information that "could not have been
obtained by observation from outside," id., at 714-715, rather than any thought processes
that flowed from such monitoring.
Footnote 4
This view comports with that of all the Courts of Appeals that have resolved the
issue. See 190 F. 3d 1041 (CA9 1999); United States v. Robinson, 62 F. 3d 1325 (CA11
1995) (upholding warrantless use of thermal imager); United States v. Myers, 46 F.
3d 668 (CA7 1995) (same); United States v. Ishmael, 48 F. 3d 850 (CA5 1995) (same);
United States v. Pinson, 24 F. 3d 1056 (CA8 1994) (same). But see United States v.
Cusumano, 67 F. 3d 1497 (CA10 1995) (warrantless use of thermal imager violated Fourth
Amendment), vacated and decided on other grounds, 83 F. 3d 1247 (CA10 1996) (en banc).
Footnote 5
The record describes a device that numbers close to a thousand manufactured units;
that has a predecessor numbering in the neighborhood of 4,000 to 5,000 units; that
competes with a similar product numbering from 5,000 to 6,000 units; and that is "readily
available to the public" for commercial, personal, or law enforcement purposes, and
is just an 800-number away from being rented from "half a dozen national companies"
by anyone who wants one. App. 18. Since, by virtue of the Court's new rule, the issue
is one of first impression, perhaps it should order an evidentiary hearing to determine
whether these facts suffice to establish "general public use."
Footnote 6
The use of the latter device would be constitutional given Smith v. Maryland, 442
U. S. 735, 741 (1979), which upheld the use of pen registers to record numbers dialed
on a phone because, unlike "the listening device employed in Katz ... pen registers
do not acquire the contents of communications."