United States v. Cuevas-Perez

In the

United States Court of Appeals
For the Seventh Circuit

No. 10-1473

U NITED S TATES OF A MERICA,
Plaintiff-Appellee,
v.

JUAN M ANUEL C UEVAS-P EREZ,
Defendant-Appellant.

Appeal from the United States District Court
for the Southern District of Illinois.
No. 09-CR-40009—G. Patrick Murphy, Judge.

A RGUED S EPTEMBER 23, 2010—D ECIDED A PRIL 28, 2011

Before C UDAHY, FLAUM and W OOD , Circuit Judges.
C UDAHY, Circuit Judge. Juan Cuevas-Perez appeals
from the denial of his motion to suppress evidence, on
the grounds that the warrantless use by law enforcement
of a Global Positioning System (“GPS”) tracking device
violated his Fourth Amendment rights. Consistent with
this circuit’s existing precedent, we agree that the sup-
pression motion should have been denied, and accord-
ingly, we affirm.
2 No. 10-1473

I. Facts and Procedural History
The facts of this case are not in dispute. In 2008, federal
Immigration and Customs Enforcement (ICE) agents,
working with local Phoenix police, came to suspect
Juan Cuevas-Perez of being involved in a drug distribu-
tion operation. They installed a pole camera outside
Cuevas-Perez’s home, and its footage revealed Cuevas-
Perez manipulating the hatch and rear door panels of
his Jeep Laredo SUV (Jeep). At approximately noon on
February 6, 2009, Phoenix detective Matthew Shay
attached a GPS tracking unit to the Jeep while it was
parked in a public area. No warrant was obtained for
the GPS installation. The GPS device was programmed
to send Detective Shay text message updates of its loca-
tion every four minutes.
Shortly after the GPS installation, Cuevas-Perez em-
barked on a road trip that took him through New
Mexico, Texas, Oklahoma and Missouri, and ultimately
into Illinois. Sometime on February 8, while Cuevas-Perez
was in Missouri, Detective Shay learned that the batteries
in the GPS device were running low. Not wanting to
lose track of Cuevas-Perez, Detective Shay contacted
regional ICE agents and advised them of the need for
visual surveillance. Then Cuevas-Perez crossed the state
line and entered Illinois. Accordingly, the ICE agents
asked the Illinois State Police (ISP) to take up surveillance.
Once they had done so, Detective Shay discontinued
the use of the GPS device; it had been in use for a total
of approximately 60 hours.
The ICE agents asked the ISP to find a reason to pull
over the defendant’s vehicle if possible. An ISP trooper
No. 10-1473 3

followed Cuevas-Perez for approximately 40 miles before
pulling him over for remaining in the left-hand passing
lane, a minor violation of Illinois traffic law.1 A drug-
detecting dog was dispatched to the scene, and the
dog indicated the possible presence of narcotics. A sub-
sequent search of the Jeep revealed nine packages of
heroin secreted in the doors and the lining of the ceiling.
The Government charged Cuevas-Perez with possession
with intent to distribute heroin in violation of 21 U.S.C.
§ 841(a)(1). Cuevas-Perez moved to suppress the drug
evidence, arguing that it had been procured in violation
of the Fourth Amendment. At the suppression hearing,
the judge indicated that he believed the result was con-
trolled by this court’s decision in United States v. Garcia,
474 F.3d 994 (7th Cir. 2007). Accordingly, the court denied
the suppression motion.
Cuevas-Perez entered a conditional guilty plea, preserv-
ing his right to appeal the suppression ruling. See Fed. R.
Crim. P. 11(a)(2). Cuevas-Perez timely appealed. He
raises three questions for our review, but given our deci-
sion it is unnecessary to reproduce them here.

II. Applicable Law
The Fourth Amendment guarantees freedom from
unreasonable search and seizure, U.S. C ONST. amend. IV,
and the Supreme Court has explained that a “search” exists
for Fourth Amendment purposes where (1) a person has

1
See 625 ILCS 5/11-701.
4 No. 10-1473

a subjective expectation of privacy, and (2) society is
willing to recognize the expectation of privacy as objec-
tively reasonable. Katz v. United States, 389 U.S. 347, 360
(1967) (Harlan, J., concurring); see also Kyllo v. United
States, 533 U.S. 27, 33 (2001).
The foundational Supreme Court precedent for
GPS-related cases is United States v. Knotts, 460 U.S. 276
(1983), which held that the use of a beeper device to
track a drug suspect did not violate the Fourth Amend-
ment because it did not amount to a search or seizure.
The Court explained that “[a] person traveling in an
automobile on public thoroughfares has no reasonable
expectation of privacy in his movements from one
place to another.” Id. at 281. In United States v. Garcia,
474 F.3d 994 (7th Cir. 2007), we considered the Fourth
Amendment implications of the installation and use of a
GPS device. In reliance on Knotts, we explained that GPS
tracking is not a search. Id. at 997 (“GPS tracking is on
the same side of the divide with . . . surveillance cameras
and . . . satellite imaging, and if what they do is not
searching in Fourth Amendment terms, neither is GPS
tracking.”). We noted in particular that GPS surveil-
lance utilizes technology to substitute “for an activity,
namely following a car on a public street, that is unequivo-
cally not a search within the meaning of the [Fourth
Amendment].” Id.2 At least two sister circuits have

2
With respect to an argument that Garcia considers only the
installation of a GPS device, and not the subsequent monitoring,
(continued...)
No. 10-1473 5

reached the same conclusion. See United States v. Marquez,
605 F.3d 604, 609-10 (8th Cir. 2010); United States v.
Pineda-Moreno, 591 F.3d 1212, 1217 (9th Cir. 2010).
An important apparently contrary precedent has been
established in the D.C. Circuit. United States v. Maynard,
615 F.3d 544 (D.C. Cir. 2010). In Maynard, the court con-
sidered the Fourth Amendment implications of the unin-
terrupted use of a GPS device for a period lasting 28
days. The court held that prolonged GPS surveillance
could amount to a search, because it may reveal more
than just the movements of a vehicle on public roads;
that is, it may reveal something approaching the
totality of a person’s lifestyle, affairs and possible
criminal activities during a long period. Id. at 558-63. The

2
(...continued)
we reject this implausibly narrow interpretation. The Garcia
court might have been more explicit about what it was and
was not deciding, but several statements make it unambiguous
that the court was discussing GPS tracking and not merely
installation. The court stated, “[t]he only issue is whether
evidence obtained as a result of a tracking device attached to
his car should have been suppressed . . . .” Id. at 995. In like
vein, the court described the relevant police conduct as a
substitute for “following a car on a public street.” Id. at 997.
That comparison applies to tracking, but not installation. A
contrary reading would imply that the court made those
statements and then affirmed Garcia’s conviction without
actually deciding whether tracking him violated the Fourth
Amendment and without a word about why the issue was
not being reached. We believe our reading is more plausible.
6 No. 10-1473

court stated in relevant part, “unlike one’s movements
during a single journey, the whole of one’s movements
over the course of a month is not actually exposed to the
public because the likelihood anyone will observe all those
movements is effectively nil.” Id. at 558 (emphasis omit-
ted).

III. Discussion
We are called on to decide whether the factually straight-
forward case before us implicates the concerns artic-
ulated in Maynard,3 or whether it is subject to the
residual principle derived from Knotts and Garcia, that
GPS tracking does not constitute a search. We believe
that the present case is not like Maynard, and accordingly,
we believe that the analysis of that case does not
apply here.
The aspects of the search in Maynard that affected the
court’s decision are absent here. The 28-day surveillance
in Maynard was much lengthier than the 60-hour sur-
veillance in the case before us. Moreover, the Maynard
court repeatedly distinguished the surveillance at issue
there from surveillance during a single journey. See
Maynard, 615 F.3d at 558, 560, 562, 565. For instance, the

3
We emphasize that, although an abundance of caution
dictates that we consider whether Maynard affects the present
case, our discussion of Maynard is not meant to approve or
disapprove the result the D.C. Circuit reached under the facts
of that case.
No. 10-1473 7

court stated, “[s]urveillance that reveals only what is
already exposed to the public—such as a person’s move-
ments during a single journey—is not a search.” Id. at
565 (citing Knotts, 460 U.S. at 285). The case before us, so
far as the record reveals, involves such a “single-trip”
duration of surveillance. Unlike in Maynard, the surveil-
lance here was not lengthy and did not expose, or risk
exposing, the twists and turns of Cuevas-Perez’s life,
including possible criminal activities, for a long period.
As the Maynard court noted, the chances that the whole
of Cuevas-Perez’s movements for a month would
actually be observed is effectively nil—but that is not
necessarily true of movements for a much shorter period.
As to the objection that the actual course of the GPS
use is not known until long after the need for a warrant
might arise, that may be true, but it is beside the point: the
need vel non for a warrant depends on the purpose of the
GPS use. And the purpose of the GPS attachment would
generally be known ex ante, even though the actual facts
of its use would only be known ex post. No different
from any other case, the police here were obliged to
decide ex ante whether their contemplated surveillance
activities would require a warrant. Here, the purpose of
the GPS was apparently only to record Cuevas-Perez’s
trip across the country from Arizona. Therefore, assuming
no significant deviation from the indicated purpose, no
warrant would be required even if the Maynard analysis
were applied. In that regard, it may be that the present
state of precedent provides only piecemeal guidance,
but this is unexceptional in the case of Fourth Amend-
8 No. 10-1473

ment issues, and is only a reason that law enforcement
may wish to obtain a warrant in close cases.
Cuevas-Perez further argues that the GPS device in his
case was different and more intrusive than those
addressed in prior cases. This argument is certainly worth
a try, since “the Supreme Court has insisted . . . that the
meaning of a Fourth Amendment search must change to
keep pace with the march of science.” Garcia, 474 F.3d
at 997 (internal citation omitted). In particular,
Cuevas-Perez points to the fact that this GPS sent (or was
capable of sending) minute-by minute messages to its
operator remotely, instead of needing to be physically
retrieved like models at issue in earlier cases. See
Pineda-Moreno, 591 F.3d at 1213; Garcia, 474 F.3d at 995.
But we are not persuaded that real-time revelation of
location (although additional to the information pro-
vided in Garcia) necessarily serves the impermissible
ends of the extensive GPS surveillance at issue in
Maynard. And looking beyond Maynard, we do not
consider this particular advancement to be significant
for Fourth Amendment purposes in general: real-time
information is exactly the kind of information that
drivers make available by traversing public roads. The
historical data gathered and stored on comparatively
primitive GPS devices is actually less akin to the pub-
licly-exposed information on which the Fourth Amend-
ment permissibility of GPS tracking is based.4

4
Several other courts have considered the distinction and found
it to be unimportant. See, e.g., State v. Sveum, 769 N.W.2d 53, 63
(continued...)
No. 10-1473 9

The use of GPS by law enforcement is a Fourth Amend-
ment frontier. Undoubtedly, future cases in the tradition
of Maynard will attempt to delineate the boundaries of
the permissible use of this technology—a technology
surely capable of abuses fit for a dystopian novel. But
the present case does not call on us to codify the limits
of allowable GPS use; indeed, in our view the case before
us cannot be distinguished from the quite recent decision
of this court in Garcia in any legally meaningful way.
Viewing the present case as controlled by that precedent,
we A FFIRM .

4
(...continued)
(Wis. Ct. App. 2009) (“It is not rational to limit the admission
of tracking information based on whether it is obtained in real
time by a signal or at a later time by direct access to the de-
vice.”), aff’d, 787 N.W.2d 317 (Wis. 2010), cert. denied, 131 S. Ct.
803 (2010); Foltz v. Commonwealth, 698 S.E.2d 281, 289-90 (Va. Ct.
App. 2010) (“Unlike here, where the GPS system auto-
matically tracked and recorded the movement of the van [in
real time], the beeper technology discussed in Knotts required
that the police follow the signal from the beeper as the con-
tainer was moved. We find that this advancement in tracking
technology provides an insufficient basis for distinguishing
Knotts.”) (internal citation omitted), reh’g en banc granted,
699 S.E.2d 522 (2010).
10 No. 10-1473

F LAUM, Circuit Judge, concurring. I share Judge Cudahy’s
view that this appeal’s outcome is governed by United
States v. Garcia, 474 F.3d 994 (7th Cir. 2007), and join the
opinion of the court to that extent. I write separately,
however, because the opinion could be read to imply
that, on different facts, we might adopt the D.C. Circuit’s
reasoning in United States v. Maynard, 615 F.3d 544 (D.C.
Cir. 2010) (reversing a denial of a motion to suppress
evidence where the government used GPS tracking for
28 days and announcing a “mosaic” conception of
Fourth Amendment searches). The dissenting opinion
of Judge Wood leaves no doubt, maintaining that
Maynard’s time is now.
I believe that Maynard is wrongly decided. The opinion
incorrectly concludes that United States v. Knotts, 460
U.S. 276 (1983) (holding that a person does not have a
reasonable expectation of privacy in movements from
one place to another on public thoroughfares), does not
apply to GPS technology. After concluding that Knotts
does not apply, the decision constructs a framework
for analyzing GPS monitoring based on an unsound
constitutional foundation.
Make no mistake, concerns over privacy in the infor-
mation era may make it appropriate to reconsider the
principles used for determining whether law enforcement
activity constitutes a search within the Fourth Amend-
ment’s meaning. The dissenting opinion cogently makes
the point. For now, however, the path for lower courts is
clear: the holding of Knotts governs GPS monitoring. The
practice of using these devices to monitor movements
No. 10-1473 11

on public roads falls squarely within the Court’s con-
sistent teaching that people do not have a legitimate
expectation of privacy in that which they reveal to third
parties or leave open to view by others. See, e.g., Florida v.
Riley, 488 U.S. 445, 449-50 (1989) (plurality opinion);
California v. Greenwood, 486 U.S. 35, 40-41 (1988); Dow Chem.
Co. v. United States, 476 U.S. 227, 238 (1986); New York v.
Class, 475 U.S. 106, 114 (1986); Smith v. Maryland, 442
U.S. 735, 743-44 (1979); Katz v. United States, 389 U.S. 347,
361 (1967) (Harlan, J., concurring) (“[O]bjects, activities,
or statements that [a person] exposes to the ‘plain view’
of outsiders are not ‘protected’ because no intention to
keep them to himself has been exhibited.”). If the
doctrine needs clarifying, tweaking, or an overhaul in
light of technologies employed by law enforcement, that
additional guidance should come from the Supreme
Court. The matter is, as they say, above our pay grade.

I.
The Fourth Amendment to the United States Constitu-
tion provides: “The right of the people to be secure in
their persons, houses, papers, and effects, against unrea-
sonable searches and seizures, shall not be violated, and
no Warrants shall issue, but upon probable cause . . . .”
U.S. C ONST. amend. IV. With few exceptions, based on
“the exigencies of the situation,” a search is unreason-
able—and therefore unlawful—if not authorized by a
search warrant. Mincey v. Arizona, 437 U.S. 385, 393-94
(1978); see also United States v. Ross, 456 U.S. 798, 809 (1982)
(automobile exception to the warrant requirement). And
12 No. 10-1473

when a search is unreasonable, the so-called exclusionary
rule kicks in to vindicate the Fourth Amendment’s
protections by kicking out the unlawfully obtained evi-
dence. See Herring v. United States, 129 S. Ct. 695, 699 (2009).
If there is no search (or seizure), however, then con-
stitutional guarantees do not come into play. And, perhaps
counterintuitively, just because law enforcement go
looking for some one or some thing does not mean that
they have conducted a search within the meaning of the
Fourth Amendment.1 To determine whether govern-
ment activity constitutes a search, well established doc-

1
Courts look to doctrine rather than the ordinary meaning of
the term “search” to figure out if law enforcement have con-
ducted a search. That may seem odd, but it (ultimately) makes
sense. In the founding era, the word meant much the same as it
means 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.” Kyllo v. United States, 533 U.S. 27, 33 n.1 (2001)
(quoting N. Webster, A N A MERICAN D ICTIONARY OF THE
E NGLISH L ANGUAGE 66 (1828) (reprint 6th ed. 1989)). As the
majority noted in Kyllo, defining search by reference to doctrine
may represent an effort to preserve the presumption that law
enforcement obtain a warrant prior to conducting searches.
However, applying doctrine to define search has little practical
effect—other than frustrating conversations with laypersons.
Even if courts looked to the ordinary meaning of the word
search to define it, courts would still have to figure out what
circumstances demand a search warrant. The Constitution is
silent on that point, so exegesis would leave dictionaries dusty
and bring us right back to doctrine.
No. 10-1473 13

trine teaches that we ask two questions; only if the
answer to both is yes has the government conducted a
search. First, we ask whether an individual “by his
conduct has exhibited an actual (subjective) expectation
of privacy.” Smith v. Maryland, 442 U.S. 735, 740 (1979)
(quotation marks omitted). The second question, where
most of the case-law action takes place, is whether the
individual’s expectation of privacy is “objectively reason-
able”—that is, whether society is willing to recognize the
expectation of privacy as reasonable. Id. The genesis of
that two-part framework is the concurring opinion,
authored by the second Justice John Marshall Harlan, in
Katz v. United States, 389 U.S. 347 (1967).
In applying the Katz framework in the context of elec-
tronic surveillance, the Court has held that people lack a
reasonable expectation of privacy in their movements
over public thoroughfares from one place to another.
That is the holding of Knotts, 460 U.S. 276; see also United
States v. Karo, 468 U.S. 705, 707 (1984) (Knotts reaches
information that could have been obtained through visual
surveillance); Illinois v. Andreas, 463 U.S. 765, 774 (1983)
(Brennan, J., dissenting) (reading Knotts more broadly
for the proposition that a person has no privacy interest
in the location of his automobile on public roads).
Leroy Knotts was arrested for his part in a methamphet-
amine operation. To nab Knotts, law enforcement used a
combination of visual surveillance and a beeper 2 to zero

2
A beeper is a radio transmitter that “emits periodic signals
that can be picked up by a receiver.” Knotts, 460 U.S. at 277.
(continued...)
14 No. 10-1473

in on a shipment of chloroform making its way from
Minneapolis, Minnesota, to Knotts’s cabin in Shell Lake,
Wisconsin. After tracking the vehicle to the cabin, law
enforcement procured a search warrant, where they found
a fully operational drug lab. Knotts, 460 U.S. at 278-79.
Knotts was arrested and convicted, and the Court’s
decision upheld the denial of his motion to suppress the
evidence against him. The Court held that a “person
travelling in an automobile on public thoroughfares has
no reasonable expectation of privacy in his movements
from one place to another.” Id. at 281. In reaching its
decision, the Court likened the use of a beeper to following
an automobile on public streets and highways, which
it presupposed did not implicate Fourth Amendment
concerns. Therefore, police—who could have maintained
visual contact with the shipment—were allowed to aug-
ment their faculties with technology, id. at 282, even
though it is more accurate to say they substituted their
faculties, for police lost visual contact during the opera-
tion, id. at 278. Yet, nothing about the effectiveness of
beepers undermined their constitutionality: “[w]e have
never equated police efficiency with constitutionality,
and we decline to do so now.” Id. at 284.
A GPS device works differently than a beeper, but
nothing inheres in the technology to take it out of

2
(...continued)
Police had installed a beeper in a container of chloroform
before the chloroform was purchased by one of Knotts’s
associates.
No. 10-1473 15

Knotts’s holding. A beeper transmits a signal that a
receiver can detect. With GPS technology, the unit itself
is a receiver: using a process called trilateration, the unit
pieces together the geographical coordinates of its
location based on its position relative to several orbiting
satellites. Renée McDonald Hutchins, Tied up in Knotts?
GPS Technology and the Fourth Amendment, 55 UCLA L. R EV
409, 415-17 (2007) (arguing that the warrant requirement
should apply to law enforcement use of GPS tracking
technology). When affixed to a vehicle, the GPS unit can
either record the vehicle’s movements for later down-
loading or transmit the information at intervals. To be
sure, GPS units are far more accurate than beepers. Com-
pare Karo, 468 U.S. at 708 (explaining that the beeper in that
case was accurate enough for officers to learn that cans
of ether were in a commercial storage facility, but not
enough to identify the locker in which the cans were
stored), with Hutchins, supra, at 420 (ever improving
GPS technology can be accurate to within roughly 6.5
feet). Yet, Knotts indicates that the precision of GPS tech-
nology does not render a person’s expectation of privacy
more reasonable: “Insofar as respondent’s complaint
appears to be simply that scientific devices such as the
beeper enabled police to be more effective in detecting
crime, it simply has no constitutional foundation.”
Knotts, 460 U.S. at 284.

II.
The D.C. Circuit’s first ambition in Maynard is to con-
clude that Knotts does not govern when police engage in
16 No. 10-1473

GPS monitoring for a prolonged period of time. The
dissent goes farther, suggesting that the intent of law
enforcement at the time the “events were unfolding,” post,
at 46, is what matters. Contra Karo, 468 U.S. at 712 (“[W]e
have never held that potential, as opposed to actual,
invasions of privacy constitute searches for purposes of
the Fourth Amendment.”). To reach its conclusion that
Knotts does not govern, the D.C. Circuit relies on dicta
from Knotts in which the Supreme Court suggested that
unspecified legal principles, different from the ones the
Court had just announced, might apply to either mass
surveillance or prolonged surveillance.
Specifically, the defendant in Knotts had argued to the
Court that removing beepers from Fourth Amendment
scrutiny would clear the way for “twenty-four hour
surveillance of any citizen of this country. . . . [A]ny person
or residence could be monitored at any time and for any
length of time.” See Brief for Respondent at 9, Knotts, 460
U.S. 276 (No. 81-1802). (At the time the concern was
science fiction; now it is all too possible.) The Supreme
Court addressed the concern by intimating that it
might reconsider its doctrine in the future. “[I]f such
dragnet type law enforcement practices as respondent
envisions should eventually occur, there will be time
enough to determine whether different constitutional
principles may be applicable.” Knotts, 460 U.S. at 284.3

3
Before and after Knotts, individual justices have concluded
in essence that the time has come, that the doctrine as imple-
(continued...)
No. 10-1473 17

Precisely what the Court was reserving in Knotts is
hardly clear. Ambiguity arises because the phrase “twenty-
four surveillance” is commonly used as shorthand for
around-the-clock surveillance over a prolonged time
period. Yet, Knotts’s concern seems to have been that any
person, perhaps every person, could be monitored by the
government. That concern seems better characterized
as mass surveillance and the concern was acknowledged
by the Court’s use of the word “dragnet.” Thus, it
appears that the Court recognized both concerns,
but whether one or both must be present to trigger
the reservation in Knotts is not self-evident. Compare
Maynard, 615 F.3d at 556-57 (Knotts reserved the issue of
prolonged 24-hour surveillance), with Garcia, 474 F.3d at
998 (reserving the issue of mass surveillance). Likewise,
the suggestion that different constitutional principles
could apply is vague. It could mean that Katz may not
be the right way to look at the question of electronic
monitoring, or it could mean that additional limiting
principles might cabin Knotts.

3
(...continued)
mented inadequately protects privacy in light of technological
advances. E.g., Dow Chem., 476 U.S. at 240 (Powell, J., concurring
in part and dissenting in part) (predicting that the majority’s
approach would “permit the gradual decay [of Fourth Amend-
ment rights] as technology advances”); see also Olmstead v.
United States, 277 U.S. 438, 473 (1928) (Brandeis, J., dissenting)
(observing that technological innovation permits the govern-
ment to learn what is “whispered in the closet” far more
effectively than by means of torture).
18 No. 10-1473

Regardless of the precise contours of Knotts’s reserva-
tion, however, I do not believe it invests lower courts
with the authority to depart from the case’s holding. The
decision in Knotts cannot fairly be read to imply that a
court could determine that the use of dragnet law enforce-
ment tactics—whatever that means—amounts to a search
under the Fourth Amendment. Rather, Knotts says that
different “constitutional principles” could apply to the
entire question of whether and when electronic mon-
itoring constitutes a search. The case holds that a person
does not have a reasonable expectation of privacy in her
movements over public thoroughfares from one place to
another. It is difficult to see—based on the case law we
have—how aggregating a nullity over a longer time
period, or for more trips, yields an expectation of privacy.
Thus, I respectfully disagree with the dissent’s conclu-
sion that the case falls outside the scope of the Supreme
Court’s rule that only it can overrule one of its precedents.
See State Oil Co. v. Khan, 522 U.S. 3, 20 (1997). The holding
in Knotts is that a person has no expectation of privacy
in movements from one place to another on public roads;
by its terms, the holding is indifferent to the technology
used to observe those movements.

III.
The fact that Knotts controls should end the inquiry.
Nonetheless, it is worth noting that Maynard’s reasoning
does not fit comfortably with the Supreme Court’s
Fourth Amendment search cases.
No. 10-1473 19

Having freed itself from Knotts, the Maynard decision
falls back on the more general framework announced by
Justice Harlan’s seminal concurrence in Katz: a person has
a legitimate expectation of privacy, and hence the Fourth
Amendment’s strictures apply, when a person’s subjec-
tive expectation of privacy is objectively reasonable. 389
U.S. at 361. The Maynard Court ruled that the defendant’s
expectation of privacy was objectively reasonable in that
case because (1) his movements during the course of a
month were not actually exposed to the public, as the
probability that someone would observe the movements
for a month was “effectively nil,” Maynard, 615 F.3d at
560, and (2) the defendant’s movements were not con-
structively exposed either because the picture that law
enforcement could obtain from one-month-long surveil-
lance revealed a whole that was greater than the sum of
its parts, id. at 561-62 (“Repeated visits to a church, a
gym, a bar, or a bookie tell a story not told by any single
visit, as does one’s not visiting any of these places over
the course of a month.”).
Neither of Maynard’s twin bases for ruling that the
defendant had an objectively reasonable expectation of
privacy is doctrinally sound—or all that workable as a
practical matter.

A.
To make the argument that the defendant’s move-
ments were not “actually exposed” to the public, Maynard
starts from the premise that “[i]n considering whether
something is ‘exposed’ to the public as that term was
20 No. 10-1473

used in Katz we ask not what another person can physi-
cally and may lawfully do but rather what a reasonable
person expects another might actually do.” 615 F.3d at
559. The probabilities premise is flawed. A person’s
expectations about actual likelihoods may indicate
whether a person had a subjective expectation of
privacy, but those expectations are not talismanic on the
question of whether a person’s expectation of privacy is
objectively reasonable. Rakas v. Illinois, 439 U.S. 128, 143
n.12 (1978) (a “legitimate” expectation of privacy “means
more than a subjective expectation of not being discov-
ered”). Take United States v. Jacobsen, 466 U.S. 109, 122 &
n.22 (1984), which held that federal agents did not con-
duct a search when they conducted a field test on cocaine
discovered by a shipping company. There, the Court said,
“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 authorities.” 466 U.S. at 122. A strictly
probabilities-based test for exposure is likewise hard
to square with cases like United States v. White, 401 U.S.
745 (1971). In White, a plurality of the Court ruled that
Katz left undisturbed the teaching in Hoffa v. United States
that the Fourth Amendment affords no protection to
“a wrongdoer’s misplaced belief that a person to whom
he voluntarily confides his wrongdoing will not reveal
it.” White, 401 U.S. at 748-49. Yet, how many people
expect that their associates are wearing wires when
they come to visit? The act is, I imagine, as unexpected
as it is unfriendly.
No. 10-1473 21

To support its conception of actual exposure, Maynard
focuses on Riley, the case in which the Court held that
police surveillance of a greenhouse within a home’s
curtilage, from an altitude of 400 feet, did not infringe
on a defendant’s reasonable expectation of privacy. In
reaching the conclusion, both the plurality and the con-
currence noted that helicopter traffic was relatively
routine. See Riley, 488 U.S. at 450, 453. It overstates the
case, however, to equate the Court’s observations about
the routineness of air travel—in the context of law enforce-
ment activity directed toward the home—as enacting a
probability-based prism for evaluating whether a
person’s expectation of privacy is reasonable. Nor does
the case support the D.C. Circuit’s apparent conclusion
that the reasonableness inquiry turns on the likelihood
that a “stranger” would make the observations in ques-
tion. See Maynard, 615 F.3d at 560.
After all, even knowing that air travel is routine, no one
actually expects that someone might hover over his
house: just as proximate cause represents a policy judg-
ment about when an outcome should be attributed
to a person’s actions, the reasonable-expectation-of-
privacy framework from Katz represents a policy
judgment (albeit by reference to society) about when the
law will honor someone’s prediction or hope that no one
is watching. One might reasonably ask whether judges
are the best actors to make that determination. See
Akhil Reed Amar, T HE B ILL OF R IGHTS: C REATION AND
R ECONSTRUCTION 70 (1998) (observing that “[j]udges and
warrants are the heavies, not the heroes, of the [Fourth
Amendment] story”). Nonetheless, the Supreme Court’s
22 No. 10-1473

case law does not indicate to me that the society will put
its imprimatur on an expectation of privacy in publicly
revealed information simply because the person thinks
no one is watching. See also Greenwood, 486 U.S. at 39-40
(“It may well be that respondents did not expect that
the contents of their garbage bags would become
known to the police or other members of the public. An ex-
pectation of privacy does not give rise to Fourth Amend-
ment protection, however, unless society is prepared
to accept that expectation as objectively reasonable.”);
Smith, 442 U.S. at 743-44 (noting that even if the peti-
tioner did expect that the phone company would keep
his calling information private, the expectation would
not be reasonable because “a person has no legitimate
expectation of privacy in information he voluntarily
turns over to third parties”).
So, Maynard’s gloss that someone’s information has not
been “actually” exposed unless it was reasonably likely
someone would gather the information and aggregate
it—which seems like another flavor of “constructive”
exposure anyway, given that police actually gathered
the publicly exposed information—seems untenable.
Under the governing legal framework, the point is not
that one expects to remain free from observation as a
probabilistic matter. The point is that, having become
aware of the fact that there are people in public spaces
who root through garbage, as in Greenwood, or that
people in aircraft might peer down from the sky, as in
Riley and California v. Ciraolo, 476 U.S. 207 (1986), a
person is not entitled to expect that he will remain
free from observation. Indeed, cases like Riley and Green-
No. 10-1473 23

wood, and Oliver v. United States, 466 U.S. 170, 177-79
(1984) (no search where police trespass into open fields
marked by no-trespassing signs), often prove striking
for law students precisely because their intuitions tell
them that a person would not expect—as a probabilistic
matter—to be subjected to the search technique in ques-
tion.
Like Riley, the Supreme Court’s limited discussion of
probabilities in Bond v. United States, 529 U.S. 334 (2000),
and Kyllo v. United States, 533 U.S. 27 (2001), do not
provide robust support for the D.C. Circuit’s conception
of the Fourth Amendment. In Bond, the Court ruled that
a defendant did not expose the contents of his soft
luggage to the public, despite the fact that it was vulnera-
ble to “tactile observation” while in an overhead bin,
because police manipulation of a bag was significantly
more invasive than the casual contact that a traveler
expects. 529 U.S. at 338-39. In Kyllo, the Court relied in
part on the fact that the thermal imaging tool that law
enforcement used to learn about activities within the
home was not in widespread public use.4 533 U.S. at 34
(emphasizing that the sanctity of the home made the
analysis relatively easy in that case). Dicta in both cases
provide arguable support for Maynard’s gloss on the

4
That point would not help Cuevas-Perez, as GPS technology
is easily obtainable and appears to be in widespread use. A
simple Internet search is nothing less than revelatory. The Orion
ST-811 used in this case is similar to publicly available counter-
parts in terms of one’s ability to keep tabs on someone in
close to real time, for extended periods of time.
24 No. 10-1473

Fourth Amendment, but the D.C. Circuit galvanizes the
dicta and elevates their doctrinal role. In Riley, Bond, and
Kyllo, law enforcement were subjecting individuals to
an investigative technique in an area where Fourth
Amendment concerns apply, or to an effect enjoying
Fourth Amendment protections. That feature matters.
Although it has become an old saw that the Fourth Amend-
ment protects people, not places, the starting point in
the Katz inquiry generally “requires reference to a
‘place,’ ” Katz, 389 U.S. at 361 (Harlan, J., concurring), or to
an effect, Bond, 529 U.S. at 336. See also Maryland v. Macon,
472 U.S. 463, 469 (1985) (individual had no expectation
of privacy in areas of a store where the public was invited
to transact business); Segura v. United States, 468 U.S.
796, 820 (1984) (“Nowhere are expectations of privacy
greater than in the home.”). Without a legitimate expecta-
tion of privacy, talk of probabilities and routineness
never gets off the ground.5

5
Maynard does point to a handful of state statutes limiting the
use of GPS devices, 615 F.3d at 564, and positive law may
give rise to a legitimate expectation of privacy, e.g., Oliver, 466
U.S. at 189 (Marshall, J., dissenting). The D.C. Circuit, however,
was correct to evince caution in relying on these state laws as
supporting a societal understanding, both because their
number is relatively small and because the case law does not
indicate that such statutes will automatically lead to
constitutionalized interests in privacy. See Jacobsen, 466 U.S. at
122 n.22 (quoting Rakas, 439 U.S. at 143-44 n.12); Greenwood,
486 U.S. at 55 n.4 (Brennan, J., dissenting) (suggesting that
(continued...)
No. 10-1473 25

In addition to its legal shortcomings, the probabilistic
“actual exposure” approach to Fourth Amendment
searches is problematic because it is unworkable. How
likely is it that a person actually would have followed
Cuevas-Perez from Texas to Illinois? To determine if it
was so unlikely that the Fourth Amendment applies, we
presumably would draw on Knotts and figure out the
likelihood that a person would be observed driving for
several hours from a city like Minneapolis, Minnesota, to
the more remote setting of Shell Lake, Wisconsin. Is
that less likely than the odds that a person would be
observed traveling from Texas to Illinois along major
highways? If a court wanted to answer that fraught
question, it would ask about the frequency with which
people take the different routes, the populations at the
endpoints in the journeys, how likely people are to peel
off at particular exits, and so forth. The framework
would prove impossible for law enforcement to admin-
ister ex ante. Kyllo, 533 U.S. at 38-39 (allowing warrantless
thermal imaging so long as no “intimate details” were
revealed would be “impractical in application” in part
because police could not know in advance whether
they were engaged in a search). And it is unlikely that
courts would prove particularly good at the task ex post,
as they would probably just rely on empirical hunches
anyway. Cf. Leonard Mlodinow, T HE D RUNKARD ’S W ALK:
H OW R ANDOMNESS R ULES O UR L IVES 37-40 (2008) (recount-

(...continued)
a statute may reinforce a right to privacy but that the statute
and right are not inextricably linked).
26 No. 10-1473

ing, and explaining the probabilities involved in, a Cali-
fornia Supreme Court case that “illustrat[es] the use
and misuse of probability in law”).
The decision in Maynard does not indicate how courts
are to decide “actual exposure” arguments, nor does
the idea have an obvious limiting principle. In-
deed, Maynard’s conception of probabilities might render
unconstitutional a great deal of bread-and-butter law
enforcement work. Few people would expect that they
are being investigated at all, much less for prolonged
periods of time, regardless of the technology at issue.
Are all prolonged investigations on the constitutional
chopping block unless police have probable cause and a
warrant? If Maynard aims at preserving traditional law
enforcement techniques while addressing legitimate
concerns about the government’s ability to use tech-
nology to peer into the lives of its citizens, its concept of
actual exposure seems to miss the mark.

B.
The other basis for Maynard’s holding that police
violated the defendant’s expectation of privacy was its
conclusion that the information about the defendant’s
movements was not “constructively” exposed to law
enforcement. (Perhaps it would have made more sense to
say that movements were constructively shielded from
view.) The idea is that law enforcement engage in a
search when their investigative activity allows them,
over the long term, to learn intimate details about a per-
son’s life. The D.C. Circuit likens the notion to a “mosaic”
No. 10-1473 27

in which law enforcement can obtain a whole picture
that is greater than the sum of its parts. Maynard, 615
F.3d at 562.
Constructive exposure is the second of Maynard’s
twin pillars, and counsel for Cuevas-Perez invoked the
concern at oral argument. The response is straight-
forward: the fact that law enforcement are able to take
information that is revealed publicly and piece together
an intimate picture of someone’s life does not raise con-
stitutional concerns under current doctrine. What
matters is that the information has been willingly con-
veyed, not that someone has aggregated it. Perhaps the
starkest exemplar of that teaching comes from the
Supreme Court’s decision in Greenwood. That is the case
in which the Supreme Court held that police do not
effect a Fourth Amendment search when they go sifting
through a person’s garbage that has been left outside
the curtilage of the home. Greenwood, 486 U.S. at 40-41. As
Justice Brennan’s dissent noted, “A single bag of trash
testifies eloquently to the eating, reading, and recrea-
tional habits of the person who produced it.” Id. at 50.
The information in a bag of trash runs the gamut,
from sexual practices to financial information to private
thoughts and everything in between. Id. The same
concerns are present with the pen registers in Smith. The
government, with a list of phone numbers in hand, could
learn much about a person’s take-out ordering habits,
the frequency of trips to the doctor’s office, and the par-
ticulars of familial relations. Of course, nothing half so
titillating was revealed by Cuevas-Perez’s journey from
Texas to Illinois, but even if intimate facts had been
28 No. 10-1473

revealed, the argument (and the D.C. Circuit’s decision
in Maynard) is difficult to reconcile with cases like Green-
wood and Smith.
In fact, other than Smith, which upheld the govern-
ment’s warrantless use of pen registers, the D.C. Circuit
cites scant Supreme Court Fourth Amendment case law
in support of its constructive exposure framework. (The
opinion suggests that the Court in Smith implicitly recog-
nized the mosaic concern, Maynard, 615 F.3d at 561, but
it is too implicit for me to perceive.) Instead, the D.C.
Circuit relies principally on a Freedom of Information
Act case, in which context the Court ruled that the con-
tents of an FBI rap sheet were exempt from disclosure
under the statute’s privacy exemption. Maynard 615 F.3d
at 561 (citing United States Dep’t of Justice v. Reporters
Comm. for Freedom of the Press, 489 U.S. 749, 764 (1989)). But
the case is inapposite, for the FOIA case tells us only
when something is private under a statute, not whether a
person has an expectation of privacy under the United
States Constitution. With respect to FOIA, the Act itself
tells us whether a person has an expectation of privacy,
based on whether the information may be withheld or
must be released. Reporters Comm., 489 U.S. at 772 (noting
that the applicability of the exemption, which allows
information constituting an “unwarranted invasion of
personal privacy” to be withheld, turns on the purposes
of FOIA). It is not obvious why we should look to FOIA
to tell us what society expects to remain private for
Fourth Amendment purposes.
The Maynard opinion also relies on state supreme
court cases which have held that GPS monitoring
No. 10-1473 29

violates state constitutional guarantees. 615 F.3d at 562.
Here, too, reliance is misplaced. Those cases acknowl-
edge that the Supreme Court has interpreted the
protections in the U.S. Constitution more narrowly
than state courts have interpreted their own constitu-
tions. See People v. Weaver, 909 N.E.2d 1195, 1202 (N.Y.
2009); State v. Jackson, 76 P.3d 217, 222 (Wash. 2003); id.
at 223-24 (finding “persuasive” the analysis in an
Oregon case that squarely conflicts with Knotts’s refusal
to consider technological efficiency in evaluating constitu-
tionality).
Moreover, the mosaic approach, like a probabilistic
“actual exposure” approach, would prove unworkable.
Law enforcement—at some point—would have to stop
looking at that which is publicly exposed. But how can
one discern the point before the fact? I do not see how,
and Maynard does not suggest answers. The case’s rea-
soning, however, suggests that the government ought to
be circumspect in using confidential informants for ex-
tended periods of time, engaging in visual surveillance
in the same areas in search of drug farms, or infiltrating
organized crime or terrorist organizations in an effort
to build a case.
Again, however, I believe that Knotts governs. Although
it is not as obvious to me as it is to my dissenting colleague
where the D.C. Circuit would draw constitutional lines
around Cuevas-Perez’s sixty-hour journey, see Maynard,
615 F.3d at 558 (suggesting that its holding would not
reach government tracking of a “single journey” by a
defendant), I do not find it necessary to ask the ques-
30 No. 10-1473

tion. Nor do I find it necessary to ask whether a rea-
sonable suspicion standard would accommodate
the competing constitutional interests at play. Cf. Karo,
468 U.S. at 718 n.5 (intimating that reasonable suspicion
might be sufficient to allow monitoring of a beeper in
the home).

IV.
New technologies and their potential to threaten privacy
may indeed raise Fourth Amendment hackles. They
certainly raise valid policy questions. (Think of the
ability of powerful computers to amass tremendous
stores of information on the public.) If we were empowered
to examine the questions surrounding GPS monitoring,
I would look to principles different from those relied
upon in Maynard—ones that more obviously speak to
the technology at issue here without suggesting the
invalidity of a host of traditional, legitimate law enforce-
ment techniques. There may be a colorable argument,
for instance, that the use of GPS technology to engage in
long-term tracking is analogous to general warrants
that the Fourth Amendment was designed to curtail,
because of the technology’s potential to be used arbitrarily
or because it may alter the relationship between citizen
and government in a way that is inimical to democratic
society. See Illinois v. Krull, 480 U.S. 340, 362 (1987)
(O’Connor, J., dissenting) (Fourth Amendment was de-
signed to curtail indiscriminate searches); Wolf v. People of
the State of Colorado, 338 U.S. 25, 27 (1949) (Frankfurter, J.)
(“The security of one’s privacy against arbitrary intrusion
by the police—which is at the core of the Fourth Amend-
No. 10-1473 31

ment—is basic to a free society.”); Thomas Y. Davies,
Recovering the Original Fourth Amendment, 98 M ICH. L. R EV.
547, 552, 657 (1999) (teaching that general warrants were
“reviled as a source of arbitrary power” and explaining
that the Founders “saw no need for a constitutional
standard to regulate the warrantless officer because they
did not perceive the warrantless officer as being capable of
posing a significant threat to the security of person or
house”); id. at 668 (at the time of the founding there was
no pressing need to regulate warrantless government
authority in part because the authority of officers was
limited); see also United States v. White, 401 U.S. 745,
762 (1971) (Douglas, J., dissenting) (“Monitoring, if preva-
lent, . . . kills free discourse . . . .”). On this view, the
constitutional ill of prolonged or mass use of GPS tech-
nology would not necessarily be based on the informa-
tion acquired by the device but on the fact of the govern-
ment’s gaze.
Of course, the Supreme Court just last term reminded
us that “[t]he judiciary risks error by elaborating too
fully on the Fourth Amendment implications of emerging
technology before its role in society has become clear.” City
of Ontario v. Quon, 130 S. Ct. 2619, 2629 (2010). In light of
Knotts’s holding and Quon’s admonition, it strikes me
not so much as insufficiently circumspect as simply
beyond our mandate to conclude that what is permis-
sible when accomplished with a beeper is impermissible
when accomplished with a GPS unit. I agree with the
dissent, however, that nothing would preclude Congress
from taking the important questions implicated by
GPS technology and imposing answers. See also Orin S.
32 No. 10-1473

Kerr, The Fourth Amendment and New Technologies: Con-
stitutional Myths and the Case for Caution, 102 M ICH. L. R EV.
801, 805-06 (2004) (arguing that Congress should be
the primary driver of privacy protections when tech-
nology “is in flux”). Indeed, the unsettled, evolving
expectations in this realm, combined with the fast pace
of technological change, may make the legislature the
branch of government that is best suited, and best
situated, to act.

W OOD , Circuit Judge, dissenting. This case presents a
critically important question about the government’s
ability constantly to monitor a person’s movements, on
and off the public streets, for an open-ended period
of time. The technological devices available for such
monitoring have rapidly attained a degree of accuracy
that would have been unimaginable to an earlier genera-
tion. They make the system that George Orwell depicted
in his famous novel, 1984, seem clumsy and easily avoid-
able by comparison. This court recognized in United States
v. Garcia, 474 F.3d 994 (7th Cir. 2007), that “the meaning of
a Fourth Amendment search must change to keep pace
with the march of science.” Id. at 997. We sensibly com-
mented further in that case that we were not closing
the door to future developments: “Whether and what
No. 10-1473 33

kind of restrictions should, in the name of the Constitu-
tion, be placed on such surveillance when used in
routine criminal enforcement are momentous issues that
fortunately we need not try to resolve in this case.” Id.
at 998.
Today we must decide whether to extend the rule
announced in Garcia, which held that the attachment of
a Global Positioning System, or GPS, tracking device on
a car did not require a warrant—when the device was
attached in public, it merely stored data, and it
was retrieved in public—should be extended to a more
sophisticated GPS tracker that transmitted at four-
minute intervals information about the vehicle’s location
to a central monitoring office for 60 hours. My colleagues
have decided that Garcia should be so extended. In
doing so, they part company with the District of
Columbia Circuit’s thought-provoking opinion in United
States v. Maynard, 615 F.3d 544 (D.C. Cir. 2010), reh’g denied
sub nom. United States v. Jones, 625 F.3d 766 (D.C. Cir. 2010).
With respect, I cannot take these steps. Although I part
ways in some respects from the reasoning adopted by
the D.C. Circuit, I would follow the ultimate conclusion
announced in Maynard and find that the police cannot
conduct a search using a device like the one here with-
out first obtaining a warrant. I would therefore reverse
the judgment of the district court.

I
I have no quarrel with a number of basic propositions
on which the majority and the concurring opinions rest.
34 No. 10-1473

First, before the Fourth Amendment enters the picture
at all, there must be something amounting to a search (or
seizure). Kyllo v. United States, 533 U.S. 27, 31 (2001).
Second, we must answer two questions in order to
decide whether a protected search has taken place: (1) does
the person have a subjective expectation of privacy
under the circumstances; and (2) is that expectation
objectively reasonable, or put differently, is it one that
society should recognize. Katz v. United States, 389 U.S.
347, 360 (1967) (Harlan, J., concurring). We all agree that
the only issue here is whether Cuevas-Perez’s expectation
of privacy met the second criterion. Third, a search is
generally unlawful if not authorized by a warrant, unless
one of the few delineated exceptions to the warrant
requirement applies. See Katz, 389 U.S. at 357.
The majority appears to take the position that there is
no “search” in any case where the government attaches
even the most sophisticated GPS device to a vehicle in
public and then activates that device so that the police
may track every movement, minute-by-minute, whether
the car is on a public road or parked in a private garage.
That means that the Fourth Amendment, in their view, has
nothing at all to say about the reasonableness of the
surveillance. If the Fourth Amendment is out of the
picture, then it makes no difference whether a police
officer subjectively had a good reason to activate a
device that he attached, if he acted on a whim, or if he
was systematically using devices put on every car in a
bad part of town to see where the drivers might be
going. The best analogy is to the lack of regulation of the
situation in which a police officer approaches a person
No. 10-1473 35

on a public street and asks a question. The officer might
be asking the question because she is bored, because
she finds the bystander attractive, because she forgot to
wear her watch and is wondering what time it is, because
she is suspicious of all persons of a particular ethnic
descent, or because the person is behaving suspiciously.
Her motivation is utterly irrelevant, as long as the en-
counter does not go beyond a consensual exchange of
words. See United States v. Childs, 277 F.3d 947, 949 (7th
Cir. 2002) (en banc). The same is true of GPS devices, under
the majority’s rule. Police officers could cruise the
parking lots of shopping malls or the streets in one of
Chicago’s rougher neighborhoods, install GPSs ran-
domly, and begin tracking any person they chose. As
long as the Fourth Amendment has no application,
nothing but the financial resources of the police depart-
ment stands between the individual person and such
tactics. I underscore this point at the outset because
the majority does not apply any Fourth Amendment
screen at all—not a “reasonable suspicion” rule, by com-
parison to Terry v. Ohio, 392 U.S. 1 (1968), and not the
normal “probable cause” rule.
Recognizing that the majority, the concurrence, and
I have no quarrel at the highest level of generality,
I confine my observations here to decisions with a more
direct bearing on our problem. At least five cases are
pertinent: United States v. Knotts, 460 U.S. 276 (1983),
United States v. Karo, 468 U.S. 705 (1984), Bond v. United
States, 529 U.S. 334 (2000), Kyllo v. United States, 533 U.S. 27
(2001), and City of Ontario v. Quon, 130 S.Ct. 2619 (2010).
36 No. 10-1473

After reviewing them, I turn to this court’s opinion in
Garcia and the D.C. Circuit’s opinion in Maynard.
In Knotts, the Supreme Court considered whether the
Fourth Amendment required the police to secure a
warrant before they could install a beeper in a drum
containing chloroform, in order to trace the movements
of the drum and thus find out where a suspected meth-
amphetamine operation was located. The respondent,
Knotts, did not challenge the installation of the device
in the container; his complaint was limited to the gov-
ernment’s use of the radio signals that the beeper trans-
mitted. By modern standards, the signals were not par-
ticularly strong. As the Supreme Court described it, the
investigating “officers followed the car in which the
chloroform had been placed, maintaining contact by
using both visual surveillance and a monitor which
received the signals sent from the beeper.” 460 U.S. at
278. In evaluating this arrangement, the Court reaffirmed
its holding in Katz to the effect that the Fourth Amend-
ment’s reach does not turn upon either the presence or
the absence of a physical intrusion into any given enclo-
sure. Knotts, 460 U.S. at 280 (quoting Katz, 389 U.S. at 353).
The activities of the officers in Knotts’s case, the Court
said, were no different from ordinary visual surveillance
along the route that the driver of the car took. Id. No
one could have thought otherwise: the officers were
tailing the car, and the only effect of the beeper was to
transmit more information to them than their unassisted
eyes and ears could have gathered. Although the Court
recognized that the officers visually lost track of the car
for a short period of time and were able to locate it
No. 10-1473 37

again only by using the signal from the beeper, it
found this fact immaterial because the officers could
have tracked the car “relying solely on their naked eyes.”
Id. at 285. The Court dismissed Knotts’s slippery-
slope argument with the following comment:
[Knotts] expresses the generalized view that the
result of the holding sought by the Government would
be that “twenty-four hour surveillance of any citizen
of this country will be possible, without judicial
knowledge or supervision.” Brief for Respondent 9
(footnote omitted). But the fact is that the “reality
hardly suggests abuse,” Zurcher v. Stanford Daily, 436
U.S. 547, 566 (1978); if such dragnet-type law enforcement
practices as respondent envisions should eventually
occur, there will be time enough then to determine whether
different constitutional principles may be applicable. Ibid.
Id. at 283-84 (emphasis added).
The Court returned to this topic only a year later in
Karo. There, it addressed two questions that Knotts had
left open: the first dealt with the installation of the beeper
device, and the second was “whether monitoring of a
beeper falls within the ambit of the Fourth Amendment
when it reveals information that could not have been
obtained through visual surveillance.” 468 U.S. at 707.
Interestingly, the government had obtained several
court orders in the case, including one authorizing the in-
stallation and monitoring of the beeper in a container of
ether that was destined to be used in a cocaine operation.
As the case reached the Supreme Court, however, concerns
with these orders led the Court to assume that both
38 No. 10-1473

the installation and monitoring were handled without a
warrant. The installation itself was of no interest: federal
authorities had placed it in their own container, and
they later substituted that container for one of respondent
Karo. As in our case, the hard question related to the
agents’ monitoring. As the Court put it, “[i]t is the ex-
ploitation of technological advances that implicates
the Fourth Amendment, not their mere existence.” Id.
at 712.
Knotts, the Court underscored, had been a case in
which both the movements of the automobile and the
arrival of the container could have been observed by the
naked eye. Id. at 713. In contrast, Karo “present[ed] the
question whether the monitoring of a beeper in a private
residence, a location not open to visual surveillance,
violates the Fourth Amendment rights of those who
have a justifiable interest in the privacy of the residence.”
Id. at 714. Providing a helpful illustration that demon-
strated the limits of the Knotts holding, the Court
answered its own question in the affirmative and found
a Fourth Amendment violation. In Karo, the reason why
the key information could not have been obtained
through visual surveillance was because it was collected
inside a private residence to which the agents had no
lawful access. That is the reason why the Court paid
particular attention to the sanctity of the home, but its
later comments make clear that it was not establishing a
rule limited to in-home searches. To the contrary, it
squarely rejected the government’s argument that “tradi-
tional justifications for the warrant requirement are
inapplicable in beeper cases.” Id. at 717. “[T]o a large
No. 10-1473 39

extent,” the Court continued, “that argument is based
upon the contention, rejected above, that the beeper
constitutes only a minuscule intrusion on protected
privacy interests.” Id.
Any doubt that the Fourth Amendment continues to
have force outside the home should have been put to rest
by the Supreme Court’s decision in Bond. In that case,
the Court held that a Border Patrol agent’s physical
manipulation of a bus passenger’s carry-on suitcase,
which had been placed openly in the overhead compart-
ment of a common-carrier bus, violated the constitu-
tional prohibition against unreasonable searches. 529
U.S. at 335. The government had argued that by exposing
his bag to the public Bond lost any reasonable expecta-
tion of privacy in it. Id. at 337. In rejecting that position,
the Court focused on how intrusive, as a practical matter,
the invasion of privacy was. A “probing tactile examina-
tion,” id., of the carry-on luggage was more intrusive
than a normal person would expect. The agent’s action,
the Court concluded, violated the Fourth Amendment.
The Court demonstrated in Kyllo that it has not con-
signed Karo and Bond to the dustbin. Kyllo presented the
question whether the Fourth Amendment was violated
by law enforcement’s use of a thermal-imaging device
aimed at a private house from a public street with the
purpose of investigating whether the heat being emitted
from the house was consistent with an illegal marijuana-
growing operation. Like the beepers in Knotts and Karo,
and like the GPS system used in Cuevas-Perez’s case,
the thermal-imaging device took advantage of new tech-
40 No. 10-1473

nology to enhance the observational powers of the police.
Writing for the Court, Justice Scalia began his analysis
with the observation that “the antecedent question
whether or not a Fourth Amendment ‘search’ has
occurred is not so simple under our precedent.” 533 U.S. at
31. For the search of a home, he continued, the analysis
is no longer tied to common-law trespass. Id. at 31-32.
And, demonstrating a cautious, case-by-case, approach
to the matter, the Court noted that it had “previously
reserved judgment as to how much technological en-
hancement of ordinary perception” from a vantage
point on a public street “is too much,” if it is the home
that is being searched. Id. at 33. It concluded as follows:
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.
Id. at 40.
The last Supreme Court decision that is pertinent to
our case is Quon, in which the Court had to decide
whether a public employee had a reasonable expectation
of privacy in text messages that he sent and received on
a pager that his employer owned and had issued to him.
In the end, it found in favor of the employer, but it re-
frained from making any sweeping statements. As
before, the Court chose instead a measured approach,
commenting that it had to “proceed with care when
considering the whole concept of privacy expectations
No. 10-1473 41

in communications made on electronic equipment
owned by a government employer. The judiciary risks
error by elaborating too fully on the Fourth Amendment
implications of emerging technology before its role in
society has become clear.” 130 S.Ct. at 2629. The Court
also acknowledged that “[r]apid changes in the dynamics
of communication and information transmission are
evident not just in the technology itself but in what
society accepts as proper behavior.” Id. Importantly,
the Court did not assume that the potential of new tech-
nologies to threaten privacy inevitably lessens rea-
sonable privacy expectations. To the contrary, the Court
emphasized that this was an open question, noting that
the pervasiveness of cell phone and text messaging tech-
nology “might strengthen the case for the expectation
of privacy.” See Quon, 130 S.Ct. at 2630. It is notable
for our purposes that it made this point not in a case
involving a search within a home, but in a case
involving Fourth Amendment rights in a public work-
place. In the end, the Court assumed for the sake of
argument that the employee did have a reasonable ex-
pectation of privacy in his text messages and that the
employer’s review of a transcript of the messages
amounted to a search for Fourth Amendment purposes.
It found, however, that the search was justified by the
special needs of the workplace and was not excessive
in scope, and so it found no constitutional violation. Id.
at 2632.
Before turning to this court’s decision in Garcia and
the relevant part of the D.C. Circuit’s decision in Maynard,
it is worth underscoring several points that emerge
42 No. 10-1473

from the Supreme Court’s cases. First, contrary to the
assumption in the concurring opinion, the Court has
never considered the Fourth Amendment implications of
the kind of GPS device that was used in Cuevas-Perez’s
case—a device whose capabilities are so far beyond
anything the Court saw in Knotts that we have difference
in kind, not just a difference in degree. There is thus no
escaping the question of how to extend these earlier
Supreme Court rulings to a new situation. See Quon, 130
S.Ct. at 2635 (Scalia, J., concurring) (“Applying the
Fourth Amendment to new technologies may sometimes
be difficult, but when it is necessary to decide a case
we have no choice.”). This is therefore not a case like
State Oil Co. v. Khan, 522 U.S. 3 (1997), in which a lower
court has before it an old question (there, whether maxi-
mum resale price maintenance agreements are subject
to antitrust’s per se rule of illegality) that the Supreme
Court had long since resolved. Second, the Court itself
has emphasized repeatedly the contextual nature of the
Fourth Amendment inquiry. It has eschewed rigid rules,
especially (as both Kyllo and Quon illustrate) where new
technologies are involved. And, taken together, even
Knotts and Karo show that certain uses of beepers (and by
extension successor technologies that perform similar
functions) may infringe legitimate expectations of privacy
sufficiently to trigger Fourth Amendment protections.
In Garcia, this court was asked to decide whether the
initial placement without a warrant of a GPS tracker on
the defendant’s car violated his Fourth Amendment
rights. At the time the device was affixed, the car was
parked on a public street; the court assumed that it was
No. 10-1473 43

also on a public street when the police retrieved it. Con-
trary to the majority’s suggestion, see ante at 4-5 n.2, the
defendant did not make a separate argument focusing
specifically on the monitoring made possible by the
GPS unit. (The majority implies that it would have been
almost silly to distinguish between the attachment of
the device and its later activation and use for monitoring,
but I find nothing absurd in such a distinction. The line
of cases I have just reviewed plainly shows that privacy
interests are normally triggered through monitoring, not
through the simple installation of the device that the
police use. And it is routine for this court to refuse to
reach out and decide issues that are not pressed by the
parties.) In Garcia, we said that the GPS device was a
substitute for an activity—following a car on a public
street—that is not protected by the Fourth Amendment,
and that the use of the GPS tracker did not transform
that activity into something illegal. 474 F.3d at 997. Even
so, we acknowledged that the new technologies differ
significantly from the older ones used by the police. “The
new technologies enable, as the old (because of expense)
do not, wholesale surveillance.” Id. at 997-98. We there-
fore recognized that certain uses of GPS devices, such
as mass surveillance, might raise a question under the
Fourth Amendment. The Garcia opinion hints, interest-
ingly, that individualized suspicion may differentiate
what is permissible under the Fourth Amendment from
“mass surveillance.” Id. at 998. The police of Polk County,
we said, had “abundant grounds for suspecting the
defendant.” Id. For all of those reasons, we rejected the
defendant’s challenge to the use of the GPS device.
44 No. 10-1473

Of the several cases around the country that have arisen
in this area, the most thoroughly reasoned is that of the
D.C. Circuit in Maynard. There, just as in Garcia, the
court had to decide whether evidence acquired through
the warrantless use of a GPS device should have been
suppressed. The police had attached the device to de-
fendant Jones’s Jeep without first obtaining a warrant.
They then proceeded to track the defendant’s move-
ments 24 hours a day for four weeks. Judge Ginsburg’s
opinion for the court began by distinguishing this kind
of search from the one that the Supreme Court had con-
sidered in Knotts. Maynard, 615 F.3d at 556. He pointed
out that the careful language in Knotts that reserved
for future consideration the constitutionality of more
extensive searches was not limited to the mass-surveillance
problem. To the contrary, the Court was also addressing
“the defendant’s argument that, if a warrant is not re-
quired, then prolonged ‘twenty-four hour surveillance
of any citizen of this country will be possible, without
judicial knowledge or supervision.’ ” Id. (quoting Knotts,
460 U.S. at 283). The GPS device in Maynard, the court
found, exposed information about the defendant to the
public that would not otherwise have been discovered:
Two considerations persuade us the information the
police discovered in this case—the totality of Jones’s
movements over the course of a month—was not
exposed to the public: First, unlike one’s move-
ments during a single journey, the whole of one’s
movements over the course of a month is not actually
exposed to the public because the likelihood anyone
will observe all those movements is effectively nil.
No. 10-1473 45

Second, the whole of one’s movements is not
exposed constructively even though each individual
movement is exposed, because that whole reveals
more—sometimes a great deal more—than does the
sum of its parts.
615 F.3d at 558. “Prolonged surveillance,” it concluded,
“reveals types of information not revealed by short-
term surveillance, such as what a person does repeatedly,
what he does not do, and what he does ensemble.” Id. at
562. Continuing, the court found that “[a] reasonable
person does not expect anyone to monitor and retain a
record of every time he drives his car, including his
origin, route, destination, and each place he stops and
how long he stays there . . . . In this way the ex-
tended recordation of a person’s movements is, like the
‘manipulation of a bus passenger’s carry-on’ canvas bag
in Bond, not what we expect anyone to do, and it
reveals more than we expect anyone to know.” 615 F.3d
at 563 (quoting Bond, 529 U.S. at 339). Finally, following
such decisions as Katz, Bond, and Kyllo, the court
concluded that the defendant’s expectation of privacy
(in the sense of freedom from prolonged GPS monitoring)
was objectively reasonable. Id. at 563-64.

II
In many ways, Cuevas-Perez’s case bears a strong
resemblance to Maynard. Agents of Immigration and
Customs Enforcement (“ICE”), working with the
Phoenix police department, watched Cuevas-Perez’s move-
ments for several days, because they believed that he
46 No. 10-1473

was smuggling cocaine. After a camera revealed that
he was fiddling around with the hatch and rear door
panels of his Jeep SUV, they decided to attach a battery-
powered GPS unit to the vehicle. Their intention was to
see where Cuevas-Perez went and to try to develop
evidence supporting their suspicions. In other words,
at the critical time (as events were unfolding, in prepara-
tion for their planned surveillance), they intended to
leave the GPS device on the car for an indefinite period
of time and conduct a search, just as the agents in
Maynard did. (To the extent that the court in Maynard
might be understood as taking an ex post view of the
reasonableness of the surveillance, I must respectfully
disagree with it. The need for a warrant must be ascer-
tained at the outset, not with the hindsight of two days’
or four weeks’ experience. See United States v. Grubbs, 547
U.S. 90, 95 (2006). I note as well that the concurring opin-
ion, ante at 16, criticizes my position for focusing on
the intent of law enforcement at the time the device
was affixed. But that is always the time when the need
for a warrant or other justification for a search is ascer-
tained. The search that follows after the warrant is
issued—or in this case the surveillance that followed after
the installation of the device—gives rise to an actual
invasion of privacy, not a potential one.)
The GPS unit that Detective Matthew Shay attached to
Cuevas-Perez’s Jeep was, as the majority concedes, de-
signed to provide constant real-time information about
the location of the vehicle to the monitoring officer. Using
satellite technology, it would send a text message pin-
pointing where the vehicle was to the mother computer
No. 10-1473 47

as often as once every minute. The unit could be, and
was, monitored from the comfort of the police officer’s
desk computer. Hoping to conserve battery life, Detec-
tive Shay decided to program it to provide location in-
formation only once every four minutes. With this infor-
mation, the detective had exactly the kind of detailed
information about Cuevas-Perez’s movements as the
authorities did in Maynard. (Interestingly, and contrary to
the majority’s assumption, the surveillance was not
necessarily limited to his movements on public roads.
Cars are commonly driven and parked on private
property, and many popular vehicles like Cuevas-Perez’s
Jeep are used off-road. This is just another way in
which the GPS empowers the police to conduct much
more intrusive surveillance than they could manage
with earlier technologies.) The only difference between
the two cases is that the battery in the device used on
Cuevas-Perez’s Jeep did not last as long as Detective Shay
had expected. At the time Shay realized this, Cuevas-
Perez had driven quite a distance, through Arizona, New
Mexico, the Texas panhandle, Oklahoma, Missouri, and
part of Illinois. To the extent that it is relevant, the major-
ity’s assertion that Cuevas-Perez’s movements in this case
can be categorized as a “single journey” under Maynard’s
reasoning, see ante at 6-7, is simply untenable. A common-
sense definition of a “single journey” encompasses, as the
D.C. Circuit observed, a trip from one’s home to the
market, not a 60-hour odyssey across 1,650 miles as was
the case here. See 615 F.3d at 560. More to the point, for
all we know, Shay may have intended to monitor the
Jeep for the same four-week period that the D.C. Circuit
48 No. 10-1473

evaluated in Maynard. It would not be the first time
that police conducted extended surveillance of a drug
dealer to find out who else was involved in the illegal
activity. But that option disappeared along with the
battery life.
Hoping to salvage the operation, Shay got in touch
first with the Missouri police and then with the Illinois
State Police and asked for assistance. ICE agents asked
the Illinois police to stop the vehicle, if they could
develop independent probable cause to do so (in other
words, if they could catch Cuevas-Perez in any kind of
traffic violation). And that is just what the Illinois State
Police did. Trooper Faulkner found Cuevas-Perez in the
passing lane and arrested him for failing to return to the
right lane within a reasonable time, as required by 625
ILCS 5/11-701. The rest is history. A trained dog alerted
to the presence of illegal drugs; officers searched the
Jeep and found the heroin; Cuevas-Perez was arrested;
and this criminal prosecution followed.

III
The lesson that I draw from the governing law that
I have reviewed, as applied to the facts of Cuevas-Perez’s
case, is that the police should have obtained a warrant
before they activated the GPS device that they had affixed
to the Jeep and began monitoring it. As I have already
explained, this does not require us to revisit the holding
of Garcia, since that case involved only the act of placing
the GPS device on a car that was out in public. I agree
with my colleagues that cases such as Karo direct us to
No. 10-1473 49

find that the simple attachment of a device on an unat-
tended car out in public is not invasive enough to
trigger the warrant requirement. 468 U.S. at 712 (observing
that “a policeman walking down a street carrying a
parabolic microphone capable of picking up conversa-
tions in nearby homes” does not engage in a search when
the microphone is off). The monitoring, however, is
qualitatively different, as we can see from the closely
analogous line of cases dealing with wiretapping.
Recall that the issue in Katz concerned electronic sur-
veillance of a telephone conversation through modernized
wiretap technology. In overturning Olmstead v. United
States, 277 U.S. 438 (1928), the Court concluded that the
“Government’s activities in electronically listening to and
recording the petitioner’s words violated the privacy
upon which he justifiably relied . . . and thus con-
stituted a ‘search and seizure’ within the meaning of the
Fourth Amendment.” Katz, 389 U.S. at 353. How the
wiretap was installed, Katz held, and whether it
involved a trespass, no longer determined whether the
government had conducted a search. Only a few months
earlier, the Court in Berger v. New York, 388 U.S. 41 (1967),
had invalidated on Fourth Amendment grounds a New
York statute authorizing the use of wiretaps. There, the
Court observed that “[f]ew threats to liberty exist which
are greater than that posed by the use of eavesdropping
devices.” Id. at 63. Noting the widespread use of wire-
taps by law enforcement authorities, the Court coun-
seled that “techniques and practices may well be devel-
oped that will operate just as speedily and certainly
and—what is more important—without attending illegal-
50 No. 10-1473

ity.” Id. These cases recognize that the monitoring of
private communications—even a conversation in a
public phone booth discussing unlawful activ-
ity—invades an individual’s reasonable expectation of
privacy. See Katz, 389 U.S. at 348. The next year, Congress
passed Title III of the Omnibus Crime Control and Safe
Street Act of 1968 to regulate wiretapping activity in
accordance with Fourth Amendment principles. All of
this built on the foundation the Court laid in Katz, and
so it is to that foundation I believe we should turn in
the present case.
Prolonged GPS surveillance, like a surreptitious wire-
tap, intrudes upon an individual’s reasonable expectation
of privacy by revealing information about her daily
trajectory and patterns that would, as a practical matter,
remain private without the aid of technology. This sort
of constant monitoring at a personal level gives rise to
precisely the “dragnet” effect the Supreme Court
identified in Knotts and decried years earlier in Berger. See
Berger, 388 U.S. at 65 (Douglas, J., concurring) (“The
traditional wiretap or electronic eavesdropping device
constitutes a dragnet, sweeping in all conversations
within its scope . . . . It intrudes upon the privacy of those
not even suspected of crime and intercepts the most
intimate of conversations.”). An officer’s monitoring of
a person’s every movement, as revealed by a GPS
tracking device, is comparable to the monitoring of phone
lines to intercept that person’s telephone conversations.
In my view, both qualify as a search under the Fourth
Amendment and both require the government to secure
a warrant before the surveillance begins (or to show that
No. 10-1473 51

an independent exception to the warrant requirement
applies). As it did in the wiretap context, Congress
could of course enact legislation to regulate GPS surveil-
lance.
To conclude that open-ended, real-time GPS surveil-
lance is not a “search” invites an unprecedented level of
government intrusion into every person’s private life.
The government could, without any metric of suspicion,
monitor the whereabouts of any person without con-
stitutional constraint. Under the majority’s view, such
surveillance is tolerable. And because the Fourth Amend-
ment protects individual rights, see District of Columbia
v. Heller, 128 S.Ct. 2783, 2790 (2008), it is not clear why
the use of GPS technology for mass surveillance would
trigger the warrant requirement if the suspicionless
surveillance of an individual does not. Thus, not only
is the indefinite GPS surveillance of a single person
permissible; the government could also keep tabs on
entire communities, perhaps with the hope of identifying
hints of criminal conduct. Under the majority’s frame-
work, GPS tracking of all cars in a high-crime area is as
unremarkable as an officer on the beat posing a polite
question to a local resident. All of this can occur solely
at the whim of a governmental actor, and there would
be no requirement to demonstrate any suspicion of wrong-
doing to a neutral magistrate.
The irony here is that the police may well have had
probable cause to conduct this intimate surveillance of
Cuevas-Perez, based on the investigation they had
already conducted. Applying the principles from the
52 No. 10-1473

wiretap cases to the situation before us, we should recog-
nize that a “search” for Fourth Amendment purposes
was taking place from the moment when the police
began monitoring this particular GPS device—one which,
as I have stressed, was capable of transmitting minute-by-
minute information, 24 hours a day. The approach that
I propose avoids any inappropriate reliance on hind-
sight; it recognizes that GPS devices entail a level of
intrusiveness on privacy expectations comparable to
that of wiretaps; and it thus concludes that society
should be prepared to recognize as reasonable the ex-
pectation that the police will not secretly be monitoring
every movement of one’s car. Finally, my approach
places no greater burden on the police to outline their
reasons for the planned surveillance than they bear in
wiretap cases. I conclude that Detective Shay conducted
a search during the time when he used this particular
GPS unit to monitor Cuevas-Perez’s location. Without
a warrant, the search was unconstitutional.
I respectfully dissent.

4-28-11