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PVAMU Fourth Amendment and the Third-Party Doctrine in the Digital Age Report

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Peter C. Ormerod†
Lawrence J. Trautman*
B.A. (magna cum laude), The George Washington
University; J.D., The George Washington University Law School.
Mr. Ormerod is an adjunct professor of business law at Western
[email protected]

B.A., The American University; MBA, The George
Washington University; J.D., Oklahoma City University School of
Law. Mr. Trautman is Assistant Professor of Business Law and
Ethics at Western Carolina University. He may be contacted at
[email protected]
The authors wish to extend particular thanks to Orin Kerr and
Stephen Henderson. All errors and omissions are our own.
There are few areas of constitutional law that raise scholars’ ire
and trouble jurists like the Fourth Amendment’s third-party
doctrine. Making sense of the Court’s distinctions between content
and metadata and between personal communications and
business records was already difficult with physical documents
and analog technologies. But the proliferation of digital
technologies has rendered obsolete the factual predicates
underpinning those distinctions, and courts have struggled
mightily with adapting third-party rules forged over thirty years
ago to new technologies.
At the same time, the Supreme Court has become more explicit
in fashioning distinct Fourth Amendment rules for digital
Electronic copy available at:
[Vol. 28.2
technologies. In a trio of 21st-century decisions, the Court has
made clear—often by overwhelming votes—that the old rules no
longer suffice.
These two strains of Fourth Amendment law are on a collision
course—a collision scheduled for the Court’s October 2017 Term.
In June 2017, the Court granted certiorari in Carpenter v. United
States, and the question presented is whether the government
needs a probable cause warrant to obtain voluminous records
about a cell phone’s location—data termed cell site location
information (CSLI)—from a wireless provider.
In this article, we first review the Court’s 21st-century digital
Fourth Amendment jurisprudence to tease out the Court’s
differential treatment of digital technologies. We then turn to the
existing third-party doctrine and attempt to make sense of the
doctrine’s distinctions between content and metadata and between
personal communications and business records. We examine how
our understanding of the existing doctrine applies to digital
information like the CSLI at issue in Carpenter. We conclude by
reviewing some types of sensitive digital information that
potentially lack Fourth Amendment protection under current
Keywords: browsing history, Carpenter v. United States, cell
phones, cell phone search, cell site locational information (CSLI),
cloud computing, constitutional law, digital data, Fourth
Amendment, Internet, iPhone, United States v. Jones, Katz v.
United States, Kyllo v. United States, location data, metadata,
United States v. Miller, privacy, Riley v. California, search
incident to arrest, Smith v. Maryland, Stored Communication Act,
Supreme Court, third-party doctrine, United States v. Wurie
JEL Classifications:
ABSTRACT ………………………………………………………………….. 73
INTRODUCTION …………………………………………………………. 76
ANALYSIS ……………………………………………………………… 78
A. The Trespass Test ………………………………………………. 78
B. The Katz Reasonable Expectation of Privacy Test … 80
C. Pre-Digital Technologies: Airborne Observation
Cases…………………………………………………………………. 81
D. Fourth Amendment Searches: The Element of
Surprise and the Probabilistic Model …………………… 83
Electronic copy available at:
A. Kyllo v. United States (2001) ………………………………. 86
1. Facts of Kyllo ………………………………………………… 86
2. The Court’s Opinion ………………………………………. 88
B. United States v. Jones (2012)………………………………. 90
1. Facts of Jones ……………………………………………….. 90
2. The Applicability of the Court’s Decision in
Knotts …………………………………………………………… 92
3. The D.C. Circuit and the Supreme Court
Majority’s Opinions ……………………………………….. 93
4. Justice Alito’s Opinion …………………………………… 95
5. Justice Sotomayor’s Opinion ………………………….. 97
C. Riley v. California and United States v. Wurie
(2014) ………………………………………………………………. 100
1. Facts of Riley and Wurie ………………………………. 101
2. Search Incident to Arrest Precedents ……………. 103
3. The Court’s Opinion …………………………………….. 105
A. Origins: Informants, Miller, and Smith………………. 111
B. Limits to the Third-Party Doctrine with Physical
Spaces and Materials………………………………………. 1144
C. Content Versus Metadata and Personal
Communications Versus Business Records …………. 116
A. Overview of the SCA …………………………………………. 120
B. Compelling Non-Content Records ………………………. 120
C. Compelling Content Records ……………………………… 121
1. Statutory Framework for Compelling Content . 121
2. The Constitutionality of Compelling Content
Under the SCA ……………………………………………. 123
DECISIONS ………………………………………………………….. 126
A. Facts and Decision Below in Carpenter v. United
States ………………………………………………………………. 127
B. Other Circuit Court Decisions Concerning CSLI …. 132
DOCTRINE …………………………………………………………… 134
A. Voluntary Conveyance and CSLI ……………………….. 135
1. Voluntary Conveyance …………………………………. 135
2. A Middle Ground: Most CSLI Is Involuntarily
Conveyed ……………………………………………………. 139
B. Participants Versus Intermediaries …………………. 1411
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[Vol. 28.2
C. Resolving Carpenter and Issues for Further
Discussion ……………………………………………………….. 145
CONCLUSION …………………………………………………………… 149
On June 5, 2017, the U.S. Supreme Court granted a writ of
certiorari in Carpenter v. United States.1 Carpenter asks whether
the government needs a probable cause warrant to obtain
voluminous records of a cell phone’s location data, which is known
as cell site location information (CSLI).2 According to Professor
Orin S. Kerr, a foremost expert on the Fourth Amendment, the
Court’s grant in Carpenter is “a momentous development,” because
“the future of surveillance law hinges on how the Supreme Court
The government currently does not need a probable cause
warrant to obtain CSLI from a telecommunication provider.
Section 2703(d) of the Stored Communications Act (SCA) provides
that the government may compel disclosure of CSLI whenever the
government offers “specific and articulable facts showing that
there are reasonable grounds to believe” that the records sought
“are relevant and material to an ongoing criminal investigation.”4
And the government uses this authority: In 2016 alone, AT&T
Wireless received over 50,000 requests for historic cell phone
location data.5 The facts of Carpenter starkly demonstrate the
scope of information the government has authority to compel
without a warrant—in this case, 127 days of the defendant’s CSLI,
about four months.6
Carpenter implicates the third-party doctrine—the rule that
1 819 F.3d 880 (6th Cir. 2016), cert. granted, 137 S. Ct. 2211 (No. 16–402)
2 Petition for Writ of Certiorari at i, 6, Carpenter v. United States, 137 S. Ct.
2211 (No. 16-402) [hereinafter Carpenter Cert. Petition].
3 Orin S. Kerr, Supreme Court agrees to hear ‘Carpenter v. United States,’ the
Fourth Amendment historical cell-site case, THE WASHINGTON POST (June 5,
4 Required Disclosure of Customer Communications or Records, 18 U.S.C.A.
§ 2703 (West, Westlaw through P.L. 115-117 approved 1/12/18).
5 See AT&T FEBRUARY 2017 TRANSPARENCY REPORT 4 (2017) (showing the
data for cell towers for January-June and July-December periods).
6 Carpenter Cert. Petition, supra note 2, at i; 16-402 Carpenter v. United
States (2017),
Electronic copy available at:
people lack a reasonable expectation of privacy in information that
third parties possess or know.7 The third-party doctrine is one of
the most widely disparaged constitutional rules still in force,8 and
not a single member of the current Court has participated in a
decision that expressly applied the doctrine.9 Making sense of the
Court’s distinctions between content and metadata and between
personal communications and business records was already
difficult with physical documents and analog technologies. The
rapid proliferation of digital technology has made the task
Herculean—rendering the rule’s factual predicates obsolete and
creating a vast cache of sensitive information only a subpoena
While the Court has studiously avoided addressing the viability
of the third-party doctrine in the 21st century, the Court has
become more explicit in fashioning distinct Fourth Amendment
rules for digital technologies like thermal imaging cameras, GPS
trackers, and smartphones seized incident to arrest. In this article,
we first examine this digital Fourth Amendment jurisprudence
and then try to make sense of how the third-party doctrine applies
to data like Timothy Carpenter’s CSLI. With the Court poised to
address the constitutional contours of electronic surveillance law,
we seek to provide helpful context about one of the most important
cases of the Court’s October 2017 term—and raise questions about
the Fourth Amendment status of other types of sensitive digital
This article has six parts. In part one, we describe the Court’s
traditional approach to Fourth Amendment searches. In the
second part, we discuss the Court’s recent decisions that suggest
the Fourth Amendment applies differently to digital technologies.
In part three, we describe the third-party doctrine. In the fourth
section, we explain the Stored Communications Act’s statutory
framework. In part five, we relate the facts and the Sixth Circuit’s
opinions in Carpenter case, and we review other cases addressing
how the Fourth Amendment applies to CSLI. Part six is our
descriptive analysis: We explain how we interpret the current
7 Daniel J. Solove, A Taxonomy of Privacy, 154(3) U. PA. L. REV. 477, 526
8 See Orin S. Kerr, The Case for the Third-Party Doctrine, 107 MICH. L. REV.
561, 563–64 (2009) [hereinafter Kerr, Third-Party Doctrine] (reflecting that many
scholars and state courts have begun rejecting this doctrine).
9 Stephen E. Henderson, Carpenter v. United States and the Fourth
Amendment: The Best Way Forward, WM. & MARY BILL RTS. J. (forthcoming)
[hereinafter Henderson, The Best Way Forward].
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[Vol. 28.2
third-party doctrine and how the Court might apply that standard
to CSLI. We conclude with a brief survey of other types of data
that current doctrine does not protect.
This section describes the traditional approach to the Fourth
Amendment. We begin by discussing the ways the government
conducts a search and then review how the Court responded to predigital technological advances in the 20th century.
The Fourth Amendment protects “[t]he right of the people to be
secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures.”10 The current understanding
of the two ways the government performs a Fourth Amendment
search is based on the 2012 case United States v. Jones:11 First, by
physically trespassing on a suspect’s property for the purpose of
obtaining information, and second, by violating the “reasonable
expectation of privacy” standard from Justice Harlan’s
concurrence in Katz v. United States.12
A. The Trespass Test
The Jones majority made clear that Justice Harlan’s Katz test
did not extinguish the pre-Katz rule: “The Katz reasonableexpectations test ‘has been added to, not substituted for,’ the
traditional property-based understanding of the Fourth
Amendment.”13 Under this property-based approach, the
government performs a Fourth Amendment search when its
agents physically intrude on a suspect’s private property for the
U.S. CONST. amend. IV.
United States v. Jones, 565 U.S. 400 (2012).
12 389 U.S. 347 (1967); see also Nita A. Farahany, Searching Secrets, 160(5) U.
PA. L. REV. 1239, 1246 (2012) (defining the “two-pronged privacy test”); Aya
Gruber, Garbage Pails and Puppy Dog Tails: Is that What Katz is Made of?, 41
U.C. DAVIS L. J. 781, 785–86 (2008) (describing whether a search and seizure
implicates the Fourth Amendment); Mary G. Leary, Katz on a Hot Tin Roof—
Saving the Fourth Amendment from Commercial Conditioning by Reviving
Voluntariness in Disclosures to Third Parties, 50 AM. CRIM. L. REV. 341, 342
(2013) (describing the Katz tests); Katherine J. Strandburg, Home on the Web and
Other Fourth Amendment Implications of Technosocial Change, 70 MD. L. REV.
101 (2011) (discussing Katz); Marc J. Blitz, Stanley in Cyberspace: Why the
Privacy Protection of the First Amendment Should Be More Like that of the
Fourth, 62 HASTINGS L.J. 357, 363 (2010) (further discussing Justice Harlan’s
13 Florida v. Jardines, 569 U.S. 1, 11 (2013) (quoting Jones, 565 U.S. at 409).
Electronic copy available at:
purpose of obtaining information.14 Hence, in 1928’s Olmstead v.
United States,15 the Court held that the government did not
perform a search when agents attached wiretaps to telephone
wires on public streets because “[t]here was no entry of the houses
or offices of the defendants.”16 And in Jones itself, where
government agents physically placed a GPS tracker on the
underside of the suspect’s automobile, the Court said: “The
Government physically occupied private property for the purpose
of obtaining information. We have no doubt that such a physical
intrusion would have been considered a ‘search’ within the
meaning of the Fourth Amendment when it was adopted.”17
The Court also applied the trespass test in 2013’s Florida v.
Jardines.18 In Jardines, law enforcement brought a drug-sniffing
dog onto the porch of the defendant’s home.19 The dog indicated
that it detected an illegal substance after sniffing the base of the
defendant’s front door.20 On that basis, the officers obtained a
search warrant for the defendant’s home, which revealed
marijuana plants.21
The Court held that the use of a drug-sniffing dog on the
defendant’s porch was a warrantless search because the “officers
were gathering information . . . in the curtilage of the house, which
we have held enjoys protection as part of the home itself,”22 and
because the officers “gathered that information by physically
entering and occupying the area to engage in conduct not explicitly
or implicitly permitted by the homeowner.”23
14 See Jones, 565 U.S. at 420–21. In response to Justice Alito’s concurrence,
Justice Scalia is explicit that a trespass alone does not suffice: “Trespass alone
does not qualify, but there must be conjoined with that what was present here:
an attempt to find something or to obtain information.” Id. at 408 n.5. Similarly,
Justice Scalia distinguishes the curtilage of a home from an open field: “[T]he
Government’s position gains little support from our conclusion in Oliver v. United
States, 466 U. S. 170 . . . (1984), that officers’ information-gathering intrusion on
an ‘open field’ did not constitute a Fourth Amendment search even though it was
a trespass at common law . . . . Quite simply, an open field, unlike the curtilage
of a home . . . is not one of those protected areas enumerated in the Fourth
Amendment.” Id. at 410–11.
15 277 U.S. 438 (1928).
16 Id. at 464.
17 Jones, 565 U.S. at 404–05.
18 569 U.S. 1 (2013).
19 Id. at 3–4.
20 Id. at 4.
21 Id.
22 Id. at 5–6.
23 Id. at 6.
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[Vol. 28.2
Justice Scalia’s majority opinion explicitly premised its
conclusion on only trespass grounds: “[W]e need not decide
whether the officers’ investigation of [the defendant’s] home
violated his expectation of privacy under Katz. . . . That the officers
learned what they learned only by physically intruding on [the
defendant’s] property to gather evidence is enough to establish
that a search occurred.”24
B. The Katz Reasonable Expectation of Privacy Test
Far murkier than the bright-line trespass test is Justice
Harlan’s two-factor standard from Katz. There, government
agents placed listening devices on the top of public pay phones to
eavesdrop on the defendant’s conversations.25 While no physical
trespass occurred, the Court nonetheless held that the government
had violated the defendant’s Fourth Amendment rights.26 In his
concurrence, Justice Harlan provided what has since become the
rule: “[T]here is a twofold requirement, first that a person have
exhibited an actual (subjective) expectation of privacy and, second,
that the expectation be one that society is prepared to recognize as
‘reasonable.’”27 Or as the Court put it in Bond v. United States28:
“First, we ask whether the individual, by his conduct, has
exhibited an actual expectation of privacy; that is, whether he has
shown that he sought to preserve something as private. . . .
Second, we inquire whether the individual’s expectation of privacy
is one that society is prepared to recognize as reasonable.”29
The touchstone for determining whether the government has
conducted a Fourth Amendment search is the point at which the
government exposes or obtains information that someone has
reasonably sought to keep private.30 Fourth Amendment searches,
24 Jardines, 569 U.S. at 11. In contrast, Justice Kagan’s concurring opinion—
which Justice Ginsburg and Justice Sotomayor joined and whose three votes were
all necessary to Justice Scalia’s five-vote majority—argued that the police
violated both the trespass test and Katz’s reasonable expectation of privacy test:
“Was this activity a trespass? Yes, as the Court holds today. Was it also an
invasion of privacy? Yes, that as well. The Court today treats this case under a
property rubric; I write separately to note that I could just as happily have
decided it by looking to Jardines’ privacy interests. A decision along those lines
would have looked . . . well, much like this one.” Id. at 13 (Kagan, J., concurring).
25 Katz, 389 U.S. at 348.
26 Id. at 353.
27 Id. at 361 (Harlan, J., concurring).
28 529 U.S. 334 (2000).
29 Id. at 338 (internal quotation marks omitted).
30 Orin S. Kerr, The Mosaic Theory of the Fourth Amendment, 111(3) MICH. L.
Electronic copy available at:
in short, often contain an element of surprise. The Court has held
that the government conducts a Fourth Amendment search when
its agents expose or obtain information from inside a home,31 a
car,32 a package,33 and a person’s pockets.34 In contrast, the
government does not conduct a search when its agents merely
observe the outside of property,35 observe something in plain
view,36 or observe something from a perspective frequented by the
C. Pre-Digital Technologies: Airborne Observation Cases
This latter example is worth further exploration. In three cases
from the 1980s, the Court considered how technology-enabled
human flight has impacted Fourth Amendment expectations of
privacy.38 We term these decisions the “airborne observation
cases,” and they have particular relevance in our discussion of
Kyllo, infra.
In California v. Ciraolo,39 the police received an anonymous tip
that the defendant was growing marijuana in his backyard.40
Unable to confirm the tip from the ground level due to a tall fence
encasing the backyard, two officers “secured a private plane and
flew over [the defendant’s] house at an altitude of 1,000 feet,
within navigable airspace.”41 From this perspective, the officers
identified marijuana plants growing in his backyard and
photographed the area with a 35mm camera.42 The defendant
challenged a warrant issued on the basis of the airborne
observations, but the Court rejected his arguments that the
Fourth Amendment forbade evidence collection by technologically-
REV. 311, 316–17 (2012) [hereinafter Kerr, Mosaic Theory].
31 See, e.g., Silverman v. United States, 365 U.S. 505, 511 (1961).
32 See, e.g., United States v. Ross, 456 U.S. 798, 807–09 (1982).
33 See, e.g., United States v. Jacobsen, 466 U.S. 109, 114 (1984).
34 See, e.g., Minnesota v. Dickerson, 508 U.S. 366, 378 (1993).
35 See, e.g., New York v. Class, 475 U.S. 106, 114 (1986).
36 See, e.g., Katz, 389 U.S. at 361 (Harlan, J., concurring) (explaining that the
government has not violated a reasonable expectation of privacy when
discovering what a person has “expose[d] to the ‘plain view’ of outsiders”).
37 See, e.g., California v. Ciraolo, 476 U.S. 207, 213–14 (1986); Florida v. Riley,
488 U.S. 445, 450 (1989).
38 California v. Ciraolo, 476 U.S. 207; Dow Chemical v. United States, 476 U.S.
227 (1986); Florida v. Riley, 488 U.S. 445.
39 476 U.S. 207 (1986).
40 Id. at 209.
41 Id.
42 Id.
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[Vol. 28.2
enabled human flight: “The observations . . . took place within
public navigable airspace . . . in a physically nonintrusive manner
[and] . . . [a]ny member of the public flying in this airspace who
glanced down could have seen everything that these officers
In Dow Chemical v. United States,44 federal regulators—denied
access to inspect an industrial complex—employed a commercial
aerial photographer, who used a “standard floor-mounted,
precision aerial mapping camera, to take photographs of the
facility from altitudes of 12,000, 3,000, and 1,200 feet.”45 As in
Ciraolo, the aircraft was at all times lawfully within navigable
airspace.46 Relying on Ciraolo, the Court rejected the complex
owner’s Fourth Amendment challenge.47 The Court suggested that
“surveillance of private property by using highly sophisticated
surveillance equipment not generally available to the public, such
as satellite technology, might be constitutionally proscribed
absent a warrant.”48 But, the Court held, the technology employed
here did not cross that threshold: “[T]he photographs here are not
so revealing of intimate details as to raise constitutional
In Florida v. Riley,50 the police received a tip that the defendant
was growing marijuana in a partially-enclosed greenhouse behind
his home.51 When an investigating officer discovered it was not
possible to see inside the greenhouse from the ground level, he
circled twice over the property in a helicopter at an altitude of 400
feet.52 From that perspective, the officer made naked-eye
observations of marijuana plants inside the greenhouse, and a
subsequent search—executed pursuant to a search warrant
obtained on the basis of the officer’s observations—revealed
marijuana plants growing inside the greenhouse.53 Justice White’s
plurality opinion held: “Here, the inspection was made from a
helicopter, but as is the case with fixed-wing planes, ‘private and
Id. at 213–14.
476 U.S. 227 (1986).
45 Id. at 229.
46 Id.
47 Id. at 234–36, 239.
48 Id. at 238.
49 Id.
50 488 U.S. 445 (1989).
51 Id. at 448. We refer to this 1989 case as “Florida v. Riley,” and we refer to
2014’s Riley v. California, 134 S. Ct. 2473 (2014), as merely “Riley.”
52 Id.
53 Id. at 448–49.
Electronic copy available at:
commercial flight [by helicopter] in the public airways is routine’
in this country, and there is no indication that such flights are
unheard of in [the defendant’s jurisdiction].”54
Justice O’Connor’s concurring opinion—which was necessary to
the judgment—explained that the defendant in Ciraolo did not
have a reasonable expectation of privacy “not because the airplane
was operating where it had a ‘right to be,’ but because public air
travel at 1,000 feet is a sufficiently routine part of modern life that
it is unreasonable” to expect that property “will not be observed
from the air at that altitude.”55 Note that her framing of the issue
differs from Chief Justice Burger’s in both Ciraolo and Dow
Chemical: The government’s aircrafts in those cases were
“lawfully within navigable airspace” under local law.56 Here,
however, Justice O’Connor argued that “[i]f the public rarely, if
ever, travels overhead at such altitudes, the observation cannot be
said to be from a vantage point generally used by the public and
[the defendant] cannot be said to have ‘knowingly exposed’ his
greenhouse to public view.”57 Indeed, Justice Blackmun’s dissent
recognized that five justices agreed “the reasonableness of [the
defendant’s] expectation depends, in large measure, on the
frequency of nonpolice helicopter flights at an altitude of 400
D. Fourth Amendment Searches: The Element of Surprise and
the Probabilistic Model
Justice O’Connor’s approach was later adopted by a sevenjustice majority in Bond v. United States.59 In Bond, the defendant
was riding a Greyhound bus from California to Arkansas.60 At a
required checkpoint stop in Texas, a federal border patrol agent
boarded the bus to check the immigration status of the
passengers.61 Satisfied the passengers were lawfully in the
country, the agent began to exit the bus, and along the way, he
Id. at 450 (quoting Ciraolo, 476 U.S. at 215).
Id. at 453 (O’Connor, J., concurring).
56 Dow Chemical v. United States, 476 U.S. at 229; see also Ciraolo, 476 U.S.
at 213 (“The observations . . . in this case took place within public navigable
57 Florida v. Riley, 488 U.S. at 455 (O’Connor, J., concurring) (internal
quotation marks and alterations omitted).
58 Id. at 467 (Blackmun, J., dissenting).
59 Bond v. United States, 529 U.S. 334.
60 Id. at 335.
61 Id.
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[Vol. 28.2
began squeezing the soft luggage that passengers had placed in
the overhead storage compartments.62 The agent squeezed a soft
canvas bag above the defendant’s seat and felt a “brick-like”
object.63 The defendant admitted the bag was his and agreed to
allow the agent to open it; this further inspection led the agent to
discover a “brick” of methamphetamine inside.64
The defendant argued that the government had violated a
reasonable expectation of privacy when the agent manipulated his
bag to ascertain information about its contents, and the
government responded by arguing it was objectively unreasonable
to expect that other people would not touch his bag.65 The Court
ruled for the defendant, reasoning:
[A] bus passenger clearly expects that his bag may be
handled. He does not expect that other passengers or bus
employees will, as a matter of course, feel the bag in an
exploratory manner. But this is exactly what the agent
did here. We therefore hold that the agent’s physical
manipulation of petitioner’s bag violated the Fourth
Importantly, the Court’s formulation of a reasonable expectation
of privacy did not hinge on what other passengers or bus
employees could do or what they might do—but rather what they
might actually do.67 Or, as articulated by D.C. Circuit Judge
Ginsburg in Jones, the GPS tracking case: “[W]hether something
is ‘expose[d] to the public,’ . . . depends not upon the theoretical
possibility, but upon the actual likelihood, of discovery by a
Id. at 336.
64 Id.
65 Bond v. United States, 529 U.S. at 336–37.
66 Id. at 338–39.
67 But see Illinois v. Caballes, 543 U.S. 405 (2005) (holding that the use of a
drug-sniffing dog to ascertain whether the trunk of the defendant’s car contained
marijuana was not a Fourth Amendment search). Some of the language in
Caballes is indeed difficult to reconcile with Bond. In his majority opinion, Justice
Stevens suggests that the likelihood that police would discover the drugs in the
trunk was irrelevant to the Fourth Amendment analysis: “[T]he expectation that
certain facts will not come to the attention of the authorities is not the same as
an interest in privacy that society is prepared to consider reasonable.” Id. at 408–
09 (internal quotation marks omitted) (quoting Jacobsen, 466 U.S. at 122 (“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
Electronic copy available at:
Professor Kerr has termed this method of search analysis the
“probabilistic model,”69 one of four different Fourth Amendment
models the Court routinely picks and chooses between.70 The
probabilistic inquiry “is descriptive rather than normative: it tries
to assess the likelihood that a person will be observed or a place
investigated based on prevailing social practices.”71 More
precisely, Professor Kerr explains, the probabilistic model
“protects citizens against unexpected invasions of privacy,”
because when the government “collects evidence in a way that
interferes with customs and social expectations, revealing what a
reasonable person might expect would remain hidden, it violates a
reasonable expectation of privacy.”72
In several 21st-century decisions, the Court has suggested that
distinct Fourth Amendment rules apply to digital technologies.73
68 United States v. Maynard, 615 F.3d 544, 560 (D.C. Cir. 2010) (quoting Katz,
389 U.S. at 351), aff’d sub nom. Jones, 565 U.S. 400.
69 See Kerr, Mosaic Theory, supra note 30, at 348–49 (citing Orin S. Kerr, Four
Models of Fourth Amendment Protection, 60(2) STAN. L. REV. 503, 508–12 (2007)
[hereinafter Kerr, Four Models]).
70 See Kerr, Four Models, supra note 69, at 506–07 (“Scholars and students of
Fourth Amendment law find the current approach frustrating because the courts
routinely mix and match the four models. Most Supreme Court opinions feature
multiple models to varying degrees, and they often switch from model to model
without recognizing the change”). Professor Kerr’s other three models are the
private facts model, the positive law model, and the policy model. See id. at 506.
The private facts model “asks whether the government’s conduct reveals
particularly private and personal information deserving of protection” and
“focuses on the information the government collects rather than how it is
collected.” Id. The positive law model “considers whether the government conduct
interferes with property rights or other legal standards outside the Fourth
Amendment.” Id. The positive law model has effectively been codified in recent
Supreme Court decisions—namely, Jones and Jardines—which have established
that physical trespass is its own, free-standing standard for Fourth Amendment
searches, independent of Katz’s reasonable expectation of privacy standard. The
policy model is a direct inquiry into “whether the police practice should be
regulated by the Fourth Amendment.” Id.
71 Id. at 508.
72 Id. at 509.
73 We do not purport to offer a comprehensive accounting of every digital
technology and how the Fourth Amendment may or should apply differently to
that digital technology vs. some comparable physical, mechanical, or analog
technology. For our purposes, “analog technologies” are those technologies that
(at least when they were first invented or implemented) convey or transmit
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We discuss three decisions in this section: warrantlessly aiming a
thermal imaging camera at a home in 2001’s Kyllo v. United
States;74 the warrantless Global Positioning System (GPS)
tracking of a suspect’s automobile for 28 days in 2012’s United
States v. Jones;75 and warrantlessly searching a defendant’s cell
phone incident to his arrest in 2014’s Riley v. California.76
A. Kyllo v. United States (2001)
The Court decided Kyllo v. United States in 2001, which asked
whether aiming a thermal imaging camera at a home was a Fourth
Amendment search.77 Below, we relate the facts and then discuss
the Court’s opinion.
1. Facts of Kyllo
In 1991, federal agents began to suspect that Danny Kyllo was
growing marijuana inside his home.78 Growing marijuana plants
indoors typically requires high-intensity lamps, so the federal
information in a physically measurable, continuous waveform, such as through
electric voltage. See Analog Computer, AMERICAN HERITAGE DICTIONARY,
=0&submit.y=0 (“A computer in which numerical data is represented by
measurable physical variables, such as electric voltage or the position of an
indicator.”). Telephones, fax machines, vinyl records, VHS tapes, and radio
transmitting beepers—such as the one at issue in Knotts—are prime examples of
analog technologies. “Digital technologies” are those technologies that convey or
transmit information in a discrete, binary format: ones and zeros. With digital
technologies, information is counted, rather than measured. See Digital,
ml?q=digital&submit.x=0&submit.y=0 (“Relating to or being a device that can
generate, record, process, receive, transmit, or display information that is
represented in discrete numerical form.”). VoIP calls, scanners, CDs, DVDs, and
GPS trackers are just a few examples of digital technologies, which correspond to
the aforementioned analog technologies. And throughout the discussion that
follows, we take “physical” to mean “[o]f or relating to material things: a wall that
formed a physical barrier; the physical environment.” Physical, AMERICAN
74 533 U.S. 27, 29 (2001).
75 Jones, 565 U.S. at 403.
76 134 S. Ct. 2473 (2014), decided together with, United States v. Wurie (No.
77 Kyllo v. United States, 533 U.S. at 29.
78 Id. at 29. See also Joel R. Reidenberg, Privacy in Public, 69 U. MIAMI L. REV.
141, 145 (2014); Richard Henry Seamon, Kyllo v. United States and the Partial
Ascendance of Justice Scalia’s Fourth Amendment, 79 WASH. U. L. Q. 1013, 1016
(2001); David A. Sklansky, Back to the Future: Kyllo, Katz, and Common Law, 72
MISS. L.J. 143, 169–70 (2002) (for further discussion).
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agents trained an Agema Thermovision 210 thermal imaging
camera at Kyllo’s home on one night in January 1992.79 Thermal
imaging cameras “detect infrared radiation, which virtually all
objects emit but which is not visible to the naked eye,”80 and
converts that 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.”81 The agents’ thermal imaging scan
of Kyllo’s home “took only a few minutes and was performed from
the passenger seat of [one agent’s] vehicle across the street from
the front of the house and also from the street in back of the
The scan revealed that portions of Kyllo’s home were
significantly warmer than his neighbors’ homes.83 A federal
magistrate judge issued a search warrant for Kyllo’s home based
on informants’ tips, utility bills, and the thermal imaging results.84
Execution of the search warrant revealed that Kyllo’s home hosted
an indoor marijuana-growing operation with more than 100
plants.85 After the district court denied Kyllo’s suppression motion,
he entered a conditional guilty plea and appealed.86
The U.S. Court of Appeals for the Ninth Circuit initially
remanded for an evidentiary hearing about the intrusiveness of
the agents’ thermal imaging scan of Kyllo’s home.87 The district
court upheld the validity of the warrant after finding that the
Agema 2010 “is a non-intrusive device” that “did not show any
people or activity within the walls of the structure,” that it “cannot
penetrate walls or windows to reveal conversations or human
activities,” and that “[n]o intimate details of the home were
observed.”88 A divided panel of the Ninth Circuit eventually
affirmed.89 The Supreme Court ruled in favor of Kyllo, 5-4, holding
that use of the thermal imaging camera was an unreasonable
warrantless Fourth Amendment search.90
Kyllo, 533 U.S. at 29.
Id. at 29–30.
Id. at 30.
Kyllo, 533 U.S. at 30.
United States v. Kyllo, 190 F. 3d 1041, 1047 (9th Cir. 1999).
Kyllo, 533 U.S. at 40.
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2. The Court’s Opinion
The analysis portion of Justice Scalia’s majority opinion begins
by observing that technological advances have undoubtedly
affected the degree of privacy secured by the Fourth Amendment.91
In support of that proposition, Justice Scalia cites Ciraolo,
discussed above, which recognized that “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.”92 Justice Scalia frames the issue
in Kyllo in terms of “what limits there are upon this power of
technology to shrink the realm of guaranteed privacy.”93
Within the framework of Katz’s reasonable-expectation-ofprivacy test, Justice Scalia’s majority opinion held: “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’ . . . constitutes a search—at least where (as here)
the technology in question is not in general public use.”94 The
Court rejected arguments advanced by the government and the
dissent that sought to downplay the intrusiveness of this
particular thermal imaging scan: A contrary holding “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.”95
Perhaps the narrowest reading of Kyllo focuses on two aspects
of how this case is distinct from Dow Chemical. The first aspect is
the police’s target: In Kyllo, the government used technology to
obtain otherwise inaccessible information about the inside of a
home,96 whereas the information in Dow Chemical was “an
industrial complex, which does not share the Fourth Amendment
sanctity of the home.”97 The Court pointedly noted: “In the home,
our cases show, all details are intimate details, because the entire
Id. at 33–34.
Id. at 34.
Id. (quoting Silverman v. United States., 365 U.S. at 512).
Kyllo, 533 U.S. at 35–36.
Id. at 29.
Id. at 37.
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area is held safe from prying government eyes.”98
The second aspect is the familiarity and availability of the
technology used to obtain that information: In Dow Chemical, the
government used a fixed-wing aircraft and a precise camera.99
These are undoubtedly significant technological advancements
since the Founding, but they are quite familiar and common to
twenty-first century Americans.100 In Kyllo, however, the
government used a thermal imaging camera, which Justice Scalia
repeatedly described as “technology . . . not in general public
To be sure, these two aspects are probably enough to explain the
different result in the three airborne observation cases and Kyllo.
But Justice Scalia’s opinion goes further, highlighting a concern
that digital technologies may eventually eradicate any and all
semblance of privacy—both inside the home and elsewhere.102 The
beginning of Justice Scalia’s analysis provides: “This [conclusion]
assures preservation of that degree of privacy against government
that existed when the Fourth Amendment was adopted.”103 A
broader reading focuses the Court’s appreciation that technology
potentially poses an existential threat to Fourth Amendment
privacy.104 The government argued that the thermal imaging did
not significantly compromise Kyllo’s privacy, but the Court said it
didn’t matter: “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
98 Id. The emphasis on the sanctity of the home—and the government’s
interference with an individual’s property interests—was later confirmed
through the revival of the trespass test in Jones and in the trespass test’s
application in Jardines.
99 Dow Chemical v. United States, 476 U.S. at 229.
100 The most obvious issue with this narrower interpretation is that it seems
unlikely that Justice Scalia’s analysis of Fourth Amendment protection would
hinge on how common and familiar the information-gathering technology is. Put
another way, we don’t think the result of Kyllo would be any different if, at some
point in the near future, the general public use of thermal imaging cameras
became common.
101 Kyllo, 533 U.S. at 34, 40 (“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.”).
102 Id. at 28.
103 Id. at 34.
104 Id. at 35–36 n.3. There can be little doubt Justice Scalia found potential
future technological advances vexing, demonstrated by a footnote that notes the
“ability to ‘see’ through walls and other opaque barriers is a clear, and
scientifically feasible, goal of law enforcement research and development.”
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occurred, we must take the long view, from the original meaning
of the Fourth Amendment forward.”105
The Court’s conclusion suggests that technologically-enhanced
searches are not just different as a matter of degree, but they are
different as a matter of kind: Here, the government used digital
technology to obtain information “that would previously have been
unknowable without physical intrusion.”106 The Court is thus
explicitly treating a digital, technologically-enhanced search
differently from a physical search. The concern animating this
distinction is circumvention—that the government should be
prohibited from using technology in a manner that undermines
Fourth Amendment restrictions on physical informationgathering techniques.
Justice Scalia also hints that he would not limit this line of
analysis to only prohibit obtaining information digitally that could
not have otherwise been constitutionally collected.107 Responding
to the dissent in footnote No. 2, Justice Scalia contends it is “quite
irrelevant” that similar information about the relative heat inside
Kyllo’s home could potentially have been gleaned through
constitutionally permissible alternative means, such as “by
observing snowmelt on the roof.”108 Justice Scalia argues: “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.”109 This suggestion takes on new importance
in the case discussed next.
B. United States v. Jones (2012)
The Court decided a second case about digital informationgathering in 2012’s United States v. Jones, which concerned longterm GPS tracking of the suspect’s automobile.110 Below, we relate
the facts, discuss a relevant precedent, examine the D.C. Circuit’s
opinion, and then analyze the Court’s two concurring opinions.
1. Facts of Jones
In 2004, the FBI began to suspect Antoine Jones of trafficking
Id. at 40.
See Kyllo, 533 U.S. at 40 (discussing a bright-line Fourth Amendment rule).
Id. at 35 n.2.
Jones, 565 U.S. at 402.
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in narcotics.111 Government agents placed Jones under
investigation, using techniques that included visual surveillance
of the nightclub he owned and operated, installation of a camera
focused on the nightclub’s front door, and a pen register and
wiretap on Jones’s cell phone.112 Based on information gleaned
from these investigatory techniques, FBI agents applied to the
U.S. District Court for the District of Columbia for a warrant
authorizing the use of a Global Positioning System (GPS) tracking
device on the automobile that Jones used.113
A warrant was issued, which required installation of the GPS
tracker inside the District of Columbia and within 10 days.114 On
the eleventh day and in Maryland, agents installed a GPS tracking
device on the undercarriage of Jones’s car while it was parked in a
public lot.115 In the litigation that followed, the government
conceded that its agents had not complied with the terms of the
warrant and argued that a warrant was not required.116
Over the 28 days that followed installation of the GPS tracker,
the government tracked the vehicle’s every movement.117 “By
means of signals from multiple satellites, the device established
the vehicle’s location within 50 to 100 feet, and communicated that
location by cellular phone to a Government computer. It relayed
more than 2,000 pages of data over the 4-week period.”118 At his
trial, the government introduced GPS-derived location data that
connected Jones to a stash house that contained $850,000 in cash,
97 kilograms of cocaine, and 1 kilogram of cocaine base.119 The
District Court denied most of Jones’s suppression motion for the
111 Id. See generally Peter P. Swire & Erin E. Murphy, How to Address
Standardless Discretion After Jones, OHIO STATE PUBLIC LAW WORKING PAPER NO.
177 (2012); Susan Freiwald, The Davis Good Faith Rule and Getting Answers to
the Questions Jones Left Open, 14 N.C. J.L. & TECH. 341 (2013); Mary Leary, The
Missed Opportunity of United States v. Jones: Commercial Erosion of Fourth
Amendment Protection in a Post-Google Earth World, 15 U. PA. J. CONST. L. 331
(2012); Marc McAllister, The Fourth Amendment and New Technologies: The
Misapplication of Analogical Reasoning, 36 S. ILL. U. L.J. 475 (2012) (for further
112 Jones, 565 U.S. at 402.
113 Id. at 402–03.
114 Id.
115 Id. at 403. This was not the sole instance of government agents physically
touching Jones’s car: Agents “once had to replace the [GPS] device’s battery when
the vehicle was parked in a different public lot in Maryland.” Id.
116 Id. at 403 n.1.
117 Id. at 403.
118 Jones, 565 U.S. at 403.
119 Id. at 403–04.
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GPS-derived location data.120 Jones was convicted, sentenced to
life in prison, and appealed.121
2. The Applicability of the Court’s Decision in Knotts
The District Court relied on the Court’s holding in United States
v. Knotts122 in its denial of Jones’s suppression motion.123 The
differences between Knotts and Jones are particularly
illuminating for our purposes of distinguishing between analog
and digital technologies.
In Knotts, the police were investigating the defendant for
manufacturing methamphetamine.124 Upon learning that one of
Knotts’s coconspirator would purchase a five-gallon drum of
chemicals, the police obtained the consent of the chemical vendor
to place a radio beeper inside the drum.125 As the Court explained,
“[a] beeper is a radio transmitter, usually battery operated, which
emits periodic signals that can be picked up by a radio receiver.”126
The police followed the coconspirator’s car containing the drum
from where it was purchased in Minneapolis, Minnesota, to a
secluded cabin near Shell Lake, Wisconsin, a journey of about 100
miles.127 For most of the drive, agents maintained visual contact
with the coconspirator’s vehicle, but exclusive use of the beeper
became necessary near the end of the drive.128
The Court held that no search occurred:
A person traveling in an automobile on public
thoroughfares has no reasonable expectation of privacy in
his movements from one place to another. When [the
coconspirator] traveled over the public streets, he
voluntarily conveyed to anyone who wanted to look the
fact that he was traveling over particular roads in a
particular direction, the fact of whatever stops he made,
and the fact of his final destination when he exited from
120 Id. at 403. “The District Court granted the motion only in part, suppressing
the data obtained while the vehicle was parked in the garage adjoining Jones’s
residence. It held the remaining data admissible.”
121 Id. at 404.
122 460 U.S. 276 (1983).
123 United States v. Jones, 451 F. Supp. 2d 71, 88 (D.D.C. 2006), aff’d in part,
rev’d in part sub nom. Maynard, 615 F.3d 544, aff’d Jones, 565 U.S. 400.
124 United States v. Knotts, 460 U.S. at 277.
125 Id. at 278.
126 Id. at 277.
127 Id.
128 Id. at 278–79.
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public roads onto private property.129
The District Court reasoned that the same analysis applied to
monitoring using a GPS device.130
3. The D.C. Circuit and the Supreme Court Majority’s Opinions
A panel of the U.S. Court of Appeals for the District of Columbia
Circuit unanimously reversed on the GPS Fourth Amendment
issue.131 Judge Douglas H. Ginsburg concluded that Knotts was
inapplicable because the Court “explicitly distinguished between
the limited information discovered by use of the beeper—
movements during a discrete journey—and more comprehensive
or sustained monitoring of the sort at issue in this case.”132
Specifically, Judge Ginsburg cited the following passage from
Knotts to argue that the Court had specifically reserved the
question of how the Fourth Amendment applies to the more
comprehensive type of surveillance implicated by the GPS tracker:
“[I]f 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
After finding the Court’s holding in Knotts inapplicable, Judge
Ginsburg’s Fourth Amendment inquiry asked two questions: First,
did Jones actually expose to the public his every movement in the
car over the 28-day tracking period? Second, did Jones
constructively expose to the public his every movement in the car
over the 28-day tracking period?134
In addressing whether Jones’s movements were actually
exposed, Judge Ginsburg first discussed many of the same
precedents reviewed above in section I.C—namely, Ciraolo,
Florida v. Riley, and Bond.135 In discussing these particular cases,
Judge Ginsburg asked whether the totality of Jones’s movements
might actually be observed by a member of the public.136 Judge
Id. at 281–82.
United States v. Jones (D.D.C.), 451 F. Supp. 2d at 88.
131 Maynard, 615 F.3d at 568.
132 Id. at 556 (citing Knotts, 465 U.S. at 283).
133 Knotts, 465 U.S. at 84.
134 Maynard, 615 F.3d at 558–59.
135 Id. at 559.
136 See id. (“In considering whether something is ‘exposed’ to the public as that
term was used in Katz we ask not what another person can physically and may
lawfully do but rather what a reasonable person expects another might actually
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Ginsburg answered:
[W]e hold the whole of a person’s movements over the
course of a month is not actually exposed to the public
because the likelihood a stranger would observe all those
movements is not just remote, it is essentially nil. It is one
thing for a passerby to observe or even to follow someone
during a single journey as he goes to the market or
returns home from work. It is another thing entirely for
that stranger to pick up the scent again the next day and
the day after that, week in and week out, dogging his prey
until he has identified all the places, people, amusements,
and chores that make up that person’s hitherto private
Judge Ginsburg similarly concluded that Jones’s movements were
not constructively exposed:
The whole of one’s movements over the course of a month
is not constructively exposed to the public because . . .
that whole reveals far more than the individual
movements it comprises. The difference is not one of
degree but of kind, for no single journey reveals the habits
and patterns that mark the distinction between a day in
the life and a way of life, nor the departure from a routine
that, like the dog that did not bark in the Sherlock Holmes
story, may reveal even more.138
Further, Judge Ginsburg explained why the whole was more than
merely the sum of its parts:
Prolonged surveillance 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. These types of information can each reveal
more about a person than does any individual trip viewed
in isolation. 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. The sequence of a person’s movements can reveal
still more; a single trip to a gynecologist’s office tells little
about a woman, but that trip followed a few weeks later
by a visit to a baby supply store tells a different story. A
person who knows all of another’s travels can deduce
Id. at 560.
Id. at 562.
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whether he is a weekly church goer, a heavy drinker, a
regular at the gym, an unfaithful husband, an outpatient
receiving medical treatment, an associate of particular
individuals or political groups—and not just one such fact
about a person, but all such facts.139
Considered as a collective whole, Judge Ginsburg held the 28
days of GPS monitoring was a Fourth Amendment search because
it revealed “an intimate picture of the subject’s life that he expects
no one to have—short perhaps of his spouse.”140
The D.C. Circuit denied the government’s petition for rehearing
over the dissent of four judges.141 Judge Brett Kavanaugh’s dissent
from the denial for rehearing en banc argued the government’s
interference with Jones’s property interests—when agents
warrantlessly installed the GPS tracker and changed its
batteries—constituted a Fourth Amendment search.142
A majority of the U.S. Supreme Court later adopted Judge
Kavanaugh’s suggestion.143 As discussed above in section I.A, a
five-justice majority held that the government conducted an
unreasonable, warrantless search when its agents physically
placed the GPS tracker on the underside of Jones’s vehicle.144
Justice Alito wrote an opinion concurring in the judgment, which
was joined by Justice Ginsburg, Justice Breyer, and Justice
Kagan.145 Justice Sotomayor joined Justice Scalia’s majority
opinion, but she also filed a separate concurring opinion.146 We
discuss the two concurring opinions in detail below because a close
reading suggests there are five votes to significantly alter how the
Court analyzes digitally-aggregated information that was
physically exposed to third parties.
4. Justice Alito’s Opinion
Most of Justice Alito’s opinion criticizes the majority’s revival of
the trespass test.147 At the end of his opinion, however, Justice
Maynard, 615 F.3d at 563.
141 United States v. Jones, 625 F.3d 766, 767 (D.C. Cir. 2010), denying reh’g en
banc to Maynard, 615 F.3d 544, aff’d sub nom. Jones, 565 U.S. 400.
142 United States v. Jones, 625 F.3d at 769–71 (Kavanaugh, J., dissenting).
143 See Jones, 565 U.S. at 413 (for holding).
144 Id.
145 Id. at 418 (Alito, J., concurring).
146 Id. at 413 (Sotomayor, J., concurring).
147 See id. at 424–25 (Alito, J., concurring).
[T]he Court’s reasoning largely disregards what is really important
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Alito argues that the 28 days of monitoring constituted a violation
of Katz’s reasonable-expectation-of-privacy test.148 Justice Alito’s
analysis is significantly shorter than Judge Ginsburg’s, but both
jurists seem to agree that the proper subject for the Katz inquiry
was the entire 28-day monitoring period, rather than analyzing
each individual trip in a vacuum.149
But importantly, Justice Alito and Judge Ginsburg differ on
precisely what expectation of privacy the government violated
here. Judge Ginsburg’s probabilistic analysis asked whether the
totality of Jones’s movements over 28 days might actually be
observed by a member of the public; he answered that question no
because “the likelihood a stranger would observe all those
movements is not just remote, it is essentially nil.”150 Justice
Alito’s focus is instead what society expects the police to do:
“[S]ociety’s expectation has been that law enforcement agents and
others would not—and indeed, in the main, simply could not
secretly monitor and catalogue every single movement of an
individual’s car for a very long period.”151 Professor Kerr’s
discussion of Justice Alito’s opinion explains that Justice Alito
“shift[ed] the probabilistic inquiry from what a person might
expect the public to see to what a person might expect that police
to do.”152 And Justice Alito argues—excepting “extraordinary
offenses” and “investigation[s] of unusual importance”—
comparable physical tracking and visual surveillance is “difficult
and costly and therefore rarely undertaken” because “constant
monitoring of the location of a vehicle for four weeks . . . would
have required a large team of agents, multiple vehicles, and
(the use of a GPS for the purpose of long-term tracking) and instead
attaches great significance to something that most would view as
relatively minor (attaching to the bottom of a car a small, light object
that does not interfere in any way with the car’s operation). Attaching
such an object is generally regarded as so trivial that it does not
provide a basis for recovery under modern tort law.
148 Id. at 430–31 (Alito, J., concurring).
149 Jones, 565 U.S. at 430 (Alito, J., concurring) (“[R]elatively short-term
monitoring of a person’s movements on public streets accords with expectations
of privacy that our society has recognized as reasonable. But the use of longer
term GPS monitoring in investigations of most offenses impinges on expectations
of privacy.”). See also Kerr, Mosaic Theory, supra note 30, at 327. (“Like the D.C.
Circuit, Justice Alito concluded that long-term GPS monitoring constituted a
search while short-term monitoring did not.”).
150 Maynard, 615 F.3d at 558.
151 Jones, 565 U.S. at 430 (Alito, J., concurring).
152 Kerr, Mosaic Theory, supra note 30, at 327.
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perhaps aerial assistance.”153
Justice Alito thus implicitly echoes an important aspect of
Kyllo—that digitally-enhanced searches are distinct from physical
searches. In Kyllo, Justice Scalia was perturbed that the
government used digital technology to obtain information “that
would previously have been unknowable without physical
intrusion.”154 But there is an important point of divergence
between Kyllo and Justice Alito in Jones on this issue: The crux of
the physical/digital distinction in Kyllo was that the police used a
digital technology to obtain information that they could not have
otherwise physically collected, because the information was about
the inside of the suspect’s home.155 In Jones, however, Justice Alito
seems to extend the point: It was theoretically possible the police
could use physical means that did not run afoul of the Fourth
Amendment to collect all of the same information about the
suspect’s movements.156 It would be costly and difficult, but
possible and constitutional. And yet Justice Alito seems prepared
to treat the digitally-enhanced, effortless collection of Jones’s
movements differently as a matter of kind, rather than degree.
Justice Alito’s opinion concludes by noting that it was
unnecessary to “identify with precision the point at which the
tracking of this vehicle became a search,” because “the line was
surely crossed before the 4-week mark.”157 In short, Justice Alito’s
opinion endorses drawing a line between traditional surveillance
and digitally-aggregated information, but it does not determine
where, exactly, that line lies.
5. Justice Sotomayor’s Opinion
Justice Sotomayor joined Justice Scalia’s majority opinion, but
she also wrote a separate concurrence.158 At bottom, Justice
Sotomayor agreed with both Justice Scalia and Justice Alito: This
was a search twice over—both a trespass and a violation of a
reasonable expectation of privacy.159
Jones, 565 U.S. at 429, 431 (Alito, J., concurring).
Kyllo, 533 U.S. at 50.
Id. at 34.
Jones, 565 U.S. at 422 (Alito, J., concurring).
Id. at 430 (Alito, J., concurring).
Id. at 413 (Sotomayor, J., concurring).
See id. at 414–15 (Sotomayor, J., concurring).
I join the Court’s opinion because I agree that a search within the
meaning of the Fourth Amendment occurs, at a minimum, where, as
here, the Government obtains information by physically intruding on
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Justice Sotomayor’s opinion is particularly notable in two
respects. First, Justice Sotomayor explicitly says the time has
come to revisit and alter how the third-party doctrine applies in
the digital age:
More fundamentally, it may be necessary to reconsider
the premise that an individual has no reasonable
expectation of privacy in information voluntarily
disclosed to third parties. This approach is ill suited to
the digital age, in which people reveal a great deal of
information about themselves to third parties in the
course of carrying out mundane tasks. People disclose
the phone numbers that they dial or text to their
cellular providers; the URLs that they visit and the email addresses with which they correspond to their
Internet service providers; and the books, groceries, and
medications they purchase to online retailers. . . . I for
one doubt that people would accept without complaint
the warrantless disclosure to the Government of a list
of every Web site they had visited in the last week, or
month, or year.160
Justice Sotomayor calls for the Court to “cease[] . . . treat[ing]
secrecy as a prerequisite for privacy.”161 And she goes on to endorse
a distinct approach to the third-party doctrine first raised by
Justice Marshall’s dissent in Smith v. Maryland162—that the scope
of disclosure of information to third parties should be limited to
the specific purpose for which it was disclosed:
I would not assume that all information voluntarily
disclosed to some member of the public for a limited purpose
is, for that reason alone, disentitled to Fourth Amendment
protection. See Smith, 442 U.S., at 749 (Marshall, J.,
dissenting) (“Privacy is not a discrete commodity, possessed
absolutely or not at all. Those who disclose certain facts to
a bank or phone company for a limited business purpose
need not assume that this information will be released to
a constitutionally protected area. . . . I agree with Justice Alito that, at
the very least, longer term GPS monitoring in investigations of most
offenses impinges on expectations of privacy.
(Internal quotation marks and alterations omitted).
160 Id. at 417–18 (Sotomayor, J., concurring) (citing Smith v. Maryland, 442
U.S. 735, 742 (1979) (superseded by statute); United States v. Miller, 425 U.S.
435, 443 (1976) (superseded by statute)). See infra section III for an in-depth
discussion of the third-party doctrine.
161 Id. at 418 (Sotomayor, J., concurring).
162 442 U.S. 735 (1979) (superseded by statute).
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other persons for other purposes”); see also Katz, 389 U.S.,
at 351–352 (“[W]hat [a person] seeks to preserve as private,
even in an area accessible to the public, may be
constitutionally protected”).163
The second notable aspect of Justice Sotomayor’s opinion is
how she frames the Katz inquiry. Citing the unique aspects of
precision—Justice Sotomayor argued:
I would take these attributes of GPS monitoring into
account when considering the existence of a reasonable
societal expectation of privacy in the sum of one’s public
movements. I would ask whether people reasonably
expect that their movements will be recorded and
aggregated in a manner that enables the government to
ascertain, more or less at will, their political and religious
beliefs, sexual habits, and so on.164
This focus is slightly distinct from both Judge Ginsburg’s approach
and Justice Alito’s approach. Judge Ginsburg asked what a person
expects other people might actually see;165 Justice Alito asked
what a person expects the police to do;166 and Justice Sotomayor’s
approach asked “whether police conduct collected so much
information that it enabled the government to learn about a
person’s private affairs more or less at will.”167
But most important for our purposes is that Justice
Sotomayor—more directly than Justice Scalia in Kyllo and Justice
Alito here—seems prepared to adopt a distinction between
physical and digitally-enhanced information gathering. She wrote:
“I do not regard as dispositive the fact that the Government might
obtain the fruits of GPS monitoring through lawful conventional
surveillance techniques.”168 In support of this assertion, Justice
Sotomayor cites footnote two of Justice Scalia’s Kyllo opinion—
that it was “quite irrelevant” that constitutionally permissible
observation could potentially have revealed the same information
as was obtained with a digitally-enhanced technique.169
The takeaway is that members of the Court are increasingly
Jones, 565 U.S. at 418 (Sotomayor, J., concurring).
Id. at 416 (Sotomayor, J., concurring).
165 Kerr, Mosaic Theory, supra note 30, at 324.
166 Id. at 328.
167 Id. (internal quotation marks omitted).
168 Jones, 565 U.S. at 416 (Sotomayor, J., concurring) (citing Kyllo, 533 U.S. at
35 n.2).
169 Id.
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adopting the position that digitally-enhanced techniques are
distinct from traditional, physical information-gathering
techniques. Justice Scalia’s concern in Kyllo on this point was
primarily about preventing circumvention—that the police should
not be able to obtain information through digital means that they
could not have permissibly physically collected.170 Justice Alito
here seems prepared to draw a line between constitutionally
permissible physical surveillance methods and digitally-enhanced
ones, a distinction premised on society’s expectations of the
logistical difficulties of old-fashioned surveillance.171 And Justice
Sotomayor goes further, seizing on the suggestion from Kyllo that
the simple fact the police may permissibly collect information
through physical means does not, categorically, render the digital
collection of that same information constitutional.172
The Court’s adoption of a bright-line distinction between the
physical and the digital becomes most explicit in the cases
discussed next.
C. Riley v. California and United States v. Wurie173 (2014)
The Court confronted a common question in Riley and Wurie:
“[W]hether the police may, without a warrant, search digital
information on a cell phone seized from an individual who has been
arrested.”174 Below, we first provide the facts of each case, relate
Kyllo, 533 U.S. at 34.
See id. (discussing further the digital and physical search dichotomy).
172 See Jones, 565 U.S. at 411 (making the point that a Katz analysis would still
173 728 F.3d 1 (1st Cir. 2013), aff’d sub nom. Riley, 134 S. Ct. 2473.
174 Riley, 134 S. Ct. at 2480; cf. Clark D. Cunningham, Apple and the American
Revolution: Remembering Why We Have the Fourth Amendment, 126 YALE L.J.
216 (2016) (deriving underlying principles from the history of the Fourth
Amendment and examining modern-day practices given these principles); Adam
M. Gershowitz, Password Protected? Can a Password Save Your Cell Phone from
the Search Incident to Arrest?, 96 IOWA L. REV. 1125 (2011) (considering the legal
protection offered by a password lock on an arrestee’s cell phone); Adam M.
Gershowitz, Seizing a Cell Phone Incident to Arrest: Data Extraction Devices,
Faraday Bags, or Aluminum Foil as a Solution to the Warrantless Cell Phone
Search Problem, 22 WM. & MARY BILL RTS. J. 601 (2013) (suggesting that cell
phones only be seized incident to arrest and preserved pending a search warrant);
LOCATION INFORMATION (2008) (reporting the preferences of Californians
regarding the use of retrospective location data from cell phones by law
enforcement); Matthew E. Orso, Cellular Phones, Warrantless Searches, and the
New Frontier of Fourth Amendment Jurisprudence, 50 SANTA CLARA L. REV. 183,
185 (2010) (proposing a different standard for searching cell phones incident to
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the search-incident-to-arrest (SITA) rule from three precedents,
and then discuss Chief Justice Roberts’s majority opinion.
1. Facts of Riley and Wurie
In the first case, the police stopped David Riley for a traffic
violation, which eventually led to his arrest for possession of
concealed and loaded firearms.175 A search of Riley incident to his
arrest revealed a smartphone in a pants pocket, and an officer who
accessed information on the phone noticed repeated use of a term
associated with the “Bloods” street gang.176 The Court described
Riley’s smartphone as “a cell phone with a broad range of other
functions based on advanced computing capability, large storage
capacity, and Internet connectivity.”177
Later, a detective specializing in street gangs further examined
the contents of Riley’s smartphone.178 The detective’s investigation
revealed “photographs of Riley standing in front of a car they
arrest and distinguishing between smartphones and older devices); JENNIFER M.
URBAN ET AL., MOBILE PHONES AND PRIVACY (2012) (reporting the results of a
survey concerning the type of data stored on cell phones and attitudes on privacy
of this data); Thomas K. Clancy, Fourth Amendment Satisfaction — The
“Reasonableness” of Digital Searches, 48 TEX. TECH L. REV. 37 (2015) (discussing
the impact of Riley on Fourth Amendment jurisprudence and suggesting that
traditional rules of search and seizure need rethinking).
175 Riley, 134 S. Ct. at 2480. Cf. Alan Butler, Get a Warrant: The Supreme
Court’s New Course for Digital Privacy Rights after Riley v. California, 10 DUKE
J. CONST. L. & PUB. POL’Y 83 (2014) (discussing the impact of Riley on Fourth
Amendment jurisprudence and considering its effects on related constitutional
questions); Adam M. Gershowitz, The Post-Riley Search Warrant: Search
Protocols and Particularity in Cell Phone Searches, 69(3) VAND. L. REV. 585 (2016)
(discussing the impact of Riley on lower court decisions and criticizing the
widespread practice of issuing overbroad search warrants); Matthew B. Kugler
& Lior J. Strahilevitz, The Myth of Fourth Amendment Circularity, 84 U. CHI. L.
REV. 1747 (2017) (reporting that changes in Fourth Amendment jurisprudence
has little impact on the public’s expectations of privacy); Adam Lamparello &
Charles E. MacLean, Riley v. California: Privacy Still Matters, but How Much
and in What Contexts?, 27 REGENT U.L. REV. 25 (2014) (hypothesizing how the
Court’s rationale in Riley will affect the Court’s analysis in later cases concerning
digital privacy); Richard H. McAdams, Riley’s Less Obvious Tradeoff: Forgoing
Scope-Limited Searches, 48 TEX. TECH L. REV. 97 (2015) (examining the
possibility of a warrant exception that would allow “scope-limited” search of cell
phones incident to arrest); Leslie A. Shoebotham, The Strife of Riley: The SearchIncident Consequences of Making an Easy Case Simple, 75 LA. L. REV. 29 (2014)
(criticizing Riley’s failure to address or reinforce the evidence-gathering
justification of the search-incident doctrine).
176 Riley, 134 S. Ct. at 2480.
177 Id.
178 Id.
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suspected had been involved in a shooting a few weeks earlier.”179
Riley was eventually convicted on three charges connected to that
earlier shooting.180 Before his trial, Riley argued “that the searches
of his phone violated the Fourth Amendment, because they had
been performed without a warrant and were not otherwise
justified by exigent circumstances.”181 The trial court rejected that
argument, the California Court of Appeal affirmed, and the
California Supreme Court denied Riley’s petition for review.182
In the second case, the police arrested Brima Wurie after
observing him engage in an apparent drug sale.183 The police
confiscated two cell phones from Wurie’s body in a search incident
to arrest; unlike the smartphone at issue in the companion case,
the mobile phone implicated here was a “flip phone,” which the
Court described “as a kind of phone that is flipped open for use and
that generally has a smaller range of features than a smart
Shortly after arriving at the police station, “officers noticed that
the phone was repeatedly receiving calls from a source identified
as ‘my house’ on the phone’s external screen.”185 The officers
navigated through several menus to ascertain the phone number
associated with the “my house” contact and used an online phone
directory to trace the number to an apartment building.186 A search
of that address, executed pursuant to a warrant, revealed
narcotics, firearms, and cash.187 Wurie was indicted on several
charges and “moved to suppress the evidence obtained from the
search on his apartment, arguing it was the fruit of an
unconstitutional search of his cell phone.”188 The district court
denied his motion and Wurie was convicted.189 A divided panel of
the First Circuit reversed.190
The Court unanimously ruled in favor of both defendants in an
opinion by Chief Justice Roberts.191
Id. at 2481.
Riley, 134 S. Ct. at 2481.
Riley, 134 S. Ct. at 2482.
Id. at 2479.
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2. Search Incident to Arrest Precedents
As Chief Justice Roberts relates in his opinion, the search
incident to arrest (SITA) rule is an exception to the warrant
requirement. The government has the right, “always recognized
under English and American law, to search the person of the
accused when legally arrested to discover and seize the fruits or
evidences of crime.”192 Litigation about the SITA rule has since
focused on the scope of the rule, “the extent to which officers may
search property found on or near the arrestee.”193 There are three
relevant Supreme Court precedents about the scope of the SITA
The first is Chimel v. California.194 The defendant was arrested
inside his three-bedroom home, and the police proceeded to search
the entire house, including the attic, the garage, and through the
contents of drawers.195 The Court articulated two rationales for the
SITA rule and held that neither rationale justified the scope of the
officers’ search of the defendant’s entire house.196 The first
rationale is the arresting officers’ safety: “[I]t is reasonable for the
arresting officer to search the person arrested in order to remove
any weapons that the latter might seek to use in order to resist
arrest or effect his escape.”197 The second rationale is preventing
the destruction of evidence: “[I]t is entirely reasonable for the
arresting officer to search for and seize any evidence on the
arrestee’s person in order to prevent its concealment or
Together, these two rationales provided the scope of the SITA
rule: “There is ample justification, therefore, for a search of the
arrestee’s person and the area ‘within his immediate control’—
construing that phrase to mean the area from within which he
might gain possession of a weapon or destructible evidence.”199
192 Weeks v. United States, 232 U.S. 383, 392 (1914). Cf. Wayne A. Logan, An
Exception Swallows a Rule: Police Authority to Search Incident to Arrest, 19 YALE
L. & POL’Y REV. 381 (2001) (attempting to distinguish custodial arrests from other
police encounters as a limit to the applicability of the search incident to arrest
exception); Ric Simmons, The Missed Opportunities of Riley v. California, 12 OHIO
ST. J. CRIM. L. 253 (2014) (discussing flaws and missed opportunities in Riley’s
majority opinion).
193 Riley, 134 S. Ct. at 2482–83.
194 395 U.S. 752 (1969).
195 Id. at 753–54.
196 Id. at 762–63, 768.
197 Id. at 763.
198 Id.
199 Id.
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The second case is United States v. Robinson.200 The defendant,
Robinson, was arrested for driving with a revoked license.201 The
arresting officer conducted a patdown and felt an object in
Robinson’s pocket that he could not initially identify.202 The officer
removed the object, which was a crumpled up cigarette package,
and when the officer opened it, he found narcotics inside.203 The
court below held that the search violated the Fourth Amendment
because “Robinson was unlikely to have evidence of the crime of
arrest on his person, and because it believed that extracting the
cigarette package and opening it could not be justified as part of a
protective search for weapons.”204
The Supreme Court reversed, explaining that:
[t]he authority to search the person incident to a lawful
custodial arrest, while based upon the need to disarm and
to discover evidence, does not depend on what a court may
later decide was the probability in a particular arrest
situation that weapons or evidence would in fact be found
upon the person of the suspect.205
The Court did not distinguish between a search of Robinson’s
person and the officer’s further inspection of the contents of an
object found during the search of his person. Only later, in United
States v. Chadwick,206 did the Court qualify this aspect of the SITA
rule: It was unreasonable and unconstitutional for the police to
search a 200-pound footlocker incident to arrest because it was not
“personal property . . . immediately associated with the person of
the arrestee.”207
The third and final case is Arizona v. Gant.208 Gant concerned
the scope of the SITA rule within the context of a vehicle.209 The
police had searched the passenger compartment of the vehicle
after having handcuffed and secured the defendants in patrol
414 U.S. 218 (1973).
Id. at 220.
202 Id. at 223.
203 Id.
204 Riley, 134 S. Ct. at 2483.
205 Robinson, 414 U.S. at 235.
206 433 U.S. 1 (1977).
207 Id. at 4, 15, abrogated on other grounds by California v. Acevedo, 500 U.S.
565 (1991).
208 556 U.S. 332 (2009).
209 See generally id. (finding that searching an arrestee’s vehicle after he has
been secured and the vehicle is outside his reach violates the Fourth Amendment
SITA exception).
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cars.210 The Court held that Chimel authorized a search of a vehicle
“only when the arrestee is unsecured and within reaching distance
of the passenger compartment at the time of the search.”211 But the
Court added an additional justification for the more thorough
search here: A warrantless search of the vehicle’s passenger
compartment is permissible “when it is ‘reasonable to believe
evidence relevant to the crime of arrest might be found in the
vehicle.’”212 This exception flows not from Chimel but rather from
“circumstances unique to the vehicle context.”213
3. The Court’s Opinion
Chief Justice Roberts’s analysis begins with the general Fourth
Amendment proposition that the Court “generally determine[s]
whether to exempt a given type of search from the warrant
requirement ‘by assessing, on the one hand, the degree to which it
intrudes upon an individual’s privacy and, on the other, the degree
to which it is needed for the promotion of legitimate governmental
interests.’”214 The Chief Justice notes that “a mechanical
application of Robinson might well support the warrantless
searches at issue here,” but argues that digital searches are
distinct from physical ones: “[W]hile Robinson’s categorical rule
strikes the appropriate balance in the context of physical objects,
neither of its rationales has much force with respect to digital
content on cell phones.”215
On the government interest side of the equation, the Court
asked “whether application of the search incident to arrest
doctrine to this particular category of effects would ‘untether the
rule from the justifications underlying the Chimel exception.’”216
The Court answered that question no.217 First, the Court reasoned
that with respect to an officer’s safety, “[d]igital data stored on a
Id. at 336, 344.
Id. at 343.
212 Id. (quoting Thornton v. United States, 541 U.S. 615, 632 (2004) (Scalia, J.,
213 Id.
214 Riley, 134 S. Ct. at 2484 (quoting Wyoming v. Houghton, 526 U.S. 295, 300
215 Id.
216 Id. at 2485 (quoting Gant, 556 U.S. at 343).
217 See id. at 2483–94 (explaining that Chimel’s SITA exception is to be used to
protect the safety of the police officer or preserve evidence at risk of being
destroyed when still within a defendant’s reach, and that in the present case, the
cell phone data posed no threat to the police officer and was no longer within
reach of Defendant).
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cell phone cannot itself be used as a weapon to harm an arresting
officer or to effectuate the arrestee’s escape.”218 As for the second
justification for SITA—preventing the destruction of evidence—
the government argued that digital data on a cell phone may be
“vulnerable to two types of evidence destruction unique to digital
data—remote wiping and data encryption.”219 The Court rejected
this argument.220 It reasoned that “in situations in which an arrest
might trigger a remote-wipe attempt or an officer discovers an
unlocked [and unencrypted] phone, it is not clear that the ability
to conduct a warrantless search would make much of a
The Court then turned to the privacy interests at stake. The
opinion notes that, while Robinson is the only Supreme Court
decision approving of a search of the contents of an item found on
an arrestee’s person, the Court was aware of many other cases
from Circuit Courts of Appeal, which include searches incident to
arrest of billfolds, address books, wallets, and purses.222 The
government had argued that “a search of all data stored on a cell
phone is materially indistinguishable from searches of these sorts
of physical items.”223 The Court flatly rejected that assertion: “That
is like saying a ride on horseback is materially indistinguishable
from a flight to the moon. Both are ways of getting from point A to
point B, but little else justifies lumping them together.”224
The Court then dedicated considerable space to explaining why
digital searches are categorically different from physical ones—
and make no mistake, the Court expressly held that digital
searches “differ in both a quantitative and a qualitative sense”
from searches of physical objects.225
On the quantitative differences, Chief Justice Roberts noted
that “[o]ne of the most notable distinguishing features of modern
Id. at 2485.
Id. at 2486.
220 Riley, 134 S. Ct. at 2486 (stating that the issues of remote wiping and data
encryption are neither prevalent nor would they allow for sufficient searches to
be made).
221 Id. at 2487.
222 See id. at 2488 (citing United States v. Carrion, 809 F. 2d 1120, 1123, 1128
(5th Cir. 1987); United States v. Watson, 669 F.2d 1374, 1383–84 (11th Cir. 1982);
United States v. Lee, 501 F. 2d 890, 892 (D.C. Cir. 1974)).
223 Id. (internal quotation marks omitted).
224 Id. “The term ‘cell phone’ is itself misleading shorthand; many of these devic
es are in fact minicomputers that also happen to have the capacity to be used as
a telephone.” Id. at 2489.
225 2489.
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cell phones is their immense storage capacity,” 226 and that modern
smart phones have a dizzying array of features, including camera,
video player, rolodex, calendar, tape recorder, library, diary,
albums, television, maps, and newspapers.227 This quantitative
difference in the amount of storage makes a cell phone much more
similar to the 200-pound footlocker disallowed in Chadwick than
the cigarette package permitted in Robinson.228
Chief Justice Roberts argued that the storage capacity of
modern cell phones has four interrelated consequences for privacy,
and his list is remarkable because each item suggests a bright-line
distinction between what was previously physically feasible and
what is now digitally possible.229 First, a cell phone’s collection of
many different types of information “reveal much more in
combination than any isolated record.”230 Second, the sheer
amount of storage makes a cell phone’s collection of any one type
of information far more revealing than would have been physically
possible: “The sum of an individual’s private life can be
reconstructed through a thousand photographs labeled with dates,
locations, and descriptions; the same cannot be said of a
photograph or two of loved ones tucked into a wallet.”231
Third, the amount of data contained on a cell phone has an
unprecedented temporal scope. For example, “[a] person might
carry in his pocket a slip of paper reminding him to call Mr. Jones;
he would not carry a record of all his communications with Mr.
Jones for the past several months, as would routinely be kept on a
phone.”232 Fourth and finally, Chief Justice Roberts remarked on
the proliferation and pervasiveness of these devices: “[M]any of the
more than 90% of American adults who own a cell phone keep on
their person a digital record of nearly every aspect of their lives—
from the mundane to the intimate,” and “[a]llowing the police to
scrutinize such records on a routine basis is quite different from
allowing them to search a personal item or two in the occasional
On the qualitative differences, Chief Justice Roberts discussed
how two types of extremely revealing data logged by modern cell
Riley, 134 S. Ct. at 2489.
Id. at 2484–85. 2489–90.
Id. at 2489.
Riley, 134 S. Ct. at 2489.
Id. at 2490.
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phones have changed the Fourth Amendment privacy equation:
Internet browsing history and location data. Browsing history, he
says, “could reveal an individual’s private interests or concerns—
perhaps a search for certain symptoms of a disease, coupled with
frequent visits to WebMD.”234 And “[h]istoric location information
is a standard feature on many smart phones and can reconstruct
specific movements down to the minute, not only around town but
also within a particular building.”235
Chief Justice Roberts, concluding the section of the opinion
about qualitative differences, makes explicit that digital
technology has fundamentally altered the Fourth Amendment
calculus. Quoting Learned Hand in 1926—”that it is ‘a totally
different thing to search a man’s pockets and use against him what
they contain, from ransacking his house for everything which may
incriminate him’”236—Chief Justice Roberts concludes:
If his pockets contain a cell phone, however, that is no
longer true. Indeed, a cell phone search would typically
expose to the government far more than the most
exhaustive search of a house: A phone not only contains
in digital form many sensitive records previously found in
the home; it also contains a broad array of private
information never found in a home in any form—unless
the phone is.237
There are two additional noteworthy issues that Chief Justice
Roberts’s decision discusses. The first concerns cloud computing,
which he explains “is the capacity of Internet-connected devices to
display data stored on remote servers rather than on the device
itself.”238 An aspect that becomes important for our analysis below
236 2490–91 (quoting United States v. Kirschenblatt, 16 F.2d 202, 203 (2nd
Cir. 1926)).
237 Id. at 2491.
238 Id. See, e.g., Primavera De Filippi & Smari McCarthy, Cloud Computing:
Centralization and Data Sovereignty, 3(2) EUR. J. L. & TECH. 1 (2012) (defining
and describing cloud computing); URS GASSER, CLOUD INNOVATION AND THE LAW:
ISSUES, APPROACHES, AND INTERPLAY (Research Publication No. 2014-7 2014)
(discussing the benefits of cloud computing); Paul Ohm, The Fourth Amendment
in a World Without Privacy, 81 MISS. L.J. 1309 (2012) (describing a third-party
(John M. Olin Law & Economics Working Paper No. 414 (2d series) 2008)
(discussing cloud computing and computers in general); Paul M. Schwartz,
Information Privacy in the Cloud, 161 U. PA. L. REV. 1623 (2013); Laurie B.
Serafino, ‘I Know My Rights, So You Go’n Need a Warrant for That:’ The Fourth
Amendment, Riley’s Impact, and Warrantless Searches of Third-Party Clouds, 19
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is that the government conceded, and the Court implicitly agreed,
that the SITA exception to the warrant requirement “may not be
stretched to cover . . . a search of files stored in the cloud,” because
that would be akin to “finding a key in a suspect’s pocket and
arguing that it allowed law enforcement to unlock and search a
house.”239 Professor Kerr explains that the Court’s “special concern
that allowing a cell phone search could accidentally allow a cloud
search, too” can “only make[] sense as a concern if there is Fourth
Amendment protection in stored contents in the cloud, too.”240
The final noteworthy aspect of the Court’s opinion comes in
discussion of the government’s proposed limiting principle—that
“officers could search cell phone data if they could have obtained
the same information from a pre-digital counterpart.”241 In
rejecting this suggestion, the Court reiterated just how different
digital data is:
[T]he fact that a search in the pre-digital era could have
turned up a photograph or two in a wallet does not justify
a search of thousands of photos in a digital gallery. The
fact that someone could have tucked a paper bank
statement in a pocket does not justify a search of every
bank statement from the last five years.242
The Court’s opinion is very explicit that digital searches
implicate quantitatively and qualitatively distinct privacy
interests. And, critically, the Court held that the government’s
justifications for physical searches must have their own merit
BERKELEY J. CRIM. L. 154 (2014) (considering if third-party Internet service
providers should not be denied Fourth Amendment protections); Christopher
Soghoian, Caught in the Cloud: Privacy, Encryption, and Government Back Doors
in the Web 2.0 Era, 8 J. TELECOMM. & HIGH TECH. L. 359 (2010) (discussing cloud
computing); Peter Swire, From Real-Time Intercepts to Stored Records: Why
Encryption Drives the Government to Seek Access to the Cloud, 2 INT’L DATA PRIV.
L. 200 (discussing law enforcement’s ability to access the cloud); CHRISTOPHER S.
Inst. for Law & Econ. Research Paper No. 11-15 2011) (describing “[c]loud
computing’s growing salience”); Jennifer C. Daskal, The Un-Territoriality of
Data, 125 YALE L.J. 326 (2015) (discussing generally how cloud computing
works); John G. Palfrey, The Public and the Private at the United States Border
with Cyberspace, 78(2) MISS. L. J. 241, 243 (2008) (discussing innovation in the
239 Riley, 134 S. Ct. at 2491.
240 Orin S. Kerr, The Significance of Riley, THE WASHINGTON POST (June 25,
241 Riley, 134 S. Ct. at 2493.
242 Id.
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before the same rules will be applied to digital searches.243 We do
not seek to belabor the point. There is a significant amount of
language in the Court’s decision that suggests SITA is just “the tip
of the iceberg” because “[w]e’re now in a ‘digital age,’ and quantity
of data and the ‘qualitatively different’ nature of at least some
digital records changes how the Fourth Amendment should
In sum, the Court’s evolution on digital searches began in Kyllo,
progressed in Jones, and, as Riley suggests, appears to be
accelerating further.
The “third-party doctrine” is the name courts and scholars have
given to the general rule that “if information is possessed or known
by third parties, then, for purposes of the Fourth Amendment, an
individual lacks a reasonable expectation of privacy in the
information.”245 “By disclosing to a third party, the subject gives
up all of his Fourth Amendment rights in the information
revealed.”246 Hence, under the third party doctrine, the
The Significance of Riley, supra note 240.
245 Daniel J. Solove, A Taxonomy of Privacy, 154 U. PA. L. REV. 477, 526 (2006).
See also, e.g., Jane R. Bambauer, Other People’s Papers, 94 TEX. L. REV. 205 (2015)
(discussing third parties and private individuals’ information); William Baude &
James Y. Stern, The Positive Law Model of the Fourth Amendment, 129(7) HARV.
L. REV. 1821 (2016) (discussing the Fourth Amendment and privacy); Steven M.
Bellovin et al., It’s Too Complicated: How the Internet Upends Katz, Smith, and
Electronic Surveillance Law, 30(1) HARV. J. L. & TECH. 1 (2016) [hereinafter
Bellovin, et al., It’s Too Complicated] (considering metadata and privacy);
Bernard Chao et al., Why Courts Fail to Protect Privacy: Race, Age, Bias, and
Technology, 106 CAL. L. REV. __ (2018) (reflecting that average citizens do not
fully understand the amount of access police have to their information); Thomas
P. Crocker, The Political Fourth Amendment, 88(2) WASH. U. L. REV. 303 (2010)
(describing the “third party” doctrine); David A. Harris, Riley v. California and
the Beginning of the End for the Third-Party Search Doctrine, 18 U. PA. J. CONST.
L. 895 (2016) (considering the application of the third-party doctrine to cloud
computing); Olivier Sylvain, Failing Expectations: Fourth Amendment Doctrine
in the Era of Total Surveillance, 49 WAKE FOREST L. REV. 485 (2014) (discussing
warrant requirements); Joseph T. Thai, Is Data Mining Ever a Search Under
Justice Stevens’ Fourth Amendment?, 74 FORDHAM L. REV. 1731, 1733 (2006) (“the
Court held decades ago that when we convey information to a third party, we give
up all constitutionally protected privacy in that information”). But see Monu S.
Bedi, Facebook and Interpersonal Privacy: Why the Third Party Doctrine Should
Not Apply, 54(1) B.C. L. REV. 1, 5 (2013) (considering “the concept of interpersonal
privacy to examine how to extend Fourth Amendment protection to Facebook
246 Kerr, Third-Party Doctrine, supra note 8, at 563.
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