The Qualitative Fourth Amendment: The Case for a Refined, Information-Focused Approach to Fourth Amendment Cases Involving Non-Trespassatory Government Surveillance

William & Mary Law Review William & Mary Law Review

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62 (2020-2021)

Issue 5

Article 7

4-1-2021

The Qualitative Fourth Amendment: The Case for a Re8ned, The Qualitative Fourth Amendment: The Case for a Re8ned,

Information-Focused Approach to Fourth Amendment Cases Information-Focused Approach to Fourth Amendment Cases

Involving Non-Trespassatory Government Surveillance Involving Non-Trespassatory Government Surveillance

Joshua L. Wagner

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Joshua L. Wagner,

The Qualitative Fourth Amendment: The Case for a Re8ned, Information-

Focused Approach to Fourth Amendment Cases Involving Non-Trespassatory Government

Surveillance

, 62 Wm. & Mary L. Rev. 1727 (2021), https://scholarship.law.wm.edu/wmlr/vol62/

iss5/7

Repository.

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THE QUALITATIVE FOURTH AMENDMENT:

THE CASE FOR A REFINED, INFORMATION-FOCUSED

APPROACH TO FOURTH AMENDMENT CASES INVOLVING

NONTRESPASSORY GOVERNMENT SURVEILLANCE

ABLE OF CONTENTS

INTRODUCTION ..................................... 1728

I. T

HE RELEVANT HISTORY OF FOURTH AMENDMENT

DOCTRINE ....................................... 1731

A. Katz and the “Reasonable Expectation of Privacy” .... 1732

B. Ciraolo, Riley, and Public Exposure ................ 1733

C. Recent Cases Involving Modern Technology.......... 1735

D. Carpenter v. United States in Context .............. 1737

1. The Facts of the Case .......................... 1738

2. The Court’s Holding ........................... 1739

II.

INDING A THROUGH LINE IN FOURTH AMENDMENT

DOCTRINE ....................................... 1741

A. The Many Unsatisfactory Candidates .............. 1742

B. An Effective Information-Based Approach ........... 1747

1. The Obtainable Information Approach as a Through

Line for Post-Katz Fourth Amendment Cases....... 1747

2. The Information-Based Approach as a Roadmap for

the Future ................................... 1749

a. The Continuing Relevance of the Trespass

Qualification............................... 1750

b. Defining “Surveillance Technology” ............ 1750

III.

HE THORNY THIRD-PARTY DOCTRINE ................ 1753

A. The Smith-Miller Standard ...................... 1754

B. Carpenter and Third-Party Doctrine ............... 1756

C. Third-Party Doctrine and the Obtainable

Information Standard ........................... 1758

ONCLUSION ....................................... 1760

1727

1728 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

NTRODUCTION

In his 2001 majority opinion for Kyllo v. United States, Justice

Scalia adopted his characteristic chiding tone to gently reproach

what he saw as a notably liberal departure from the original textual

interpretation of the Constitution.

The Katz test for Fourth

Amendment violations,

to Scalia, was plainly “circular, and hence

subjective and unpredictable.”

That it was one of the most influen-

tial and oft-discussed decisions the Supreme Court has ever handed

down

made little difference; regardless of whatever Justice Harlan

and his successors had said, the Fourth Amendment was, at its

heart, a protection against government interference with property

and had never been tied to “the quality or quantity of information

obtained.”

Of course, Scalia’s property-centric reproach of Katz’s legacy was

far from unprecedented. In fact, legal scholars as well respected as

Judge Richard Posner of the Seventh Circuit Court of Appeals had

been slinging the very same criticisms at the two-prong Katz test for

years.

No matter one’s opinion of either of these jurists, or of the

ubiquitous “reasonable expectation of privacy”

test, it would be

difficult to argue that it has been easy to apply in practice. And the

Court has, frustratingly, avoided directly addressing the issue.

Given this, one might be tempted to join the textualists in their

1. 533 U.S. 27, 31-40 (2001).

2. See Katz v. United States, 389 U.S. 347 (1967).

3. Kyllo, 533 U.S. at 34.

4. See T

HE SOCIAL HISTORY OF CRIME AND PUNISHMENT IN AMERICA 578 (Wilbur R. Miller

ed., 2012) (noting the influence of the Katz decision).

5. See Kyllo, 533 U.S. at 37.

6. See Richard A. Posner, The Uncertain Protection of Privacy by the Supreme Court,

1979 S

UP.CT.REV. 173, 188 (“[I]t is circular to say that there is no invasion of privacy unless

the individual whose privacy is invaded had a reasonable expectation of privacy; whether he

will or will not have such an expectation will depend on what the legal rule is.”). But see

generally Matthew B. Kugler & Lior Jacob Strahilevitz, The Myth of Fourth Amendment

Circularity, 84 U.

HI.L.REV. 1747, 1747 (2017) (“[P]opular privacy expectations are far more

stable than most judges and commentators have been assuming.”).

7. See Katz, 389 U.S. at 360 (Harlan, J., concurring).

8. Orin Kerr, Answering Justice Alito’s Question: What Makes an Expectation of Privacy

‘Reasonable’?, W

ASH.POST (May 28, 2014, 8:50 AM), https://www.washingtonpost.com/

news/volokh-conspiracy/wp/2014/05/28/answering-justice-alitos-question-what-makes-an-

expectation-of-privacy-reasonable/ [https://perma.cc/D9NR-KZAE].

2021] THE QUALITATIVE FOURTH AMENDMENT 1729

opinion that the old, easy-to-apply, property-based standard is

superior.

That does not mean, however, that the Katz test has led to

undesirable outcomes. In the age of modern technology, when the

government has access to surveillance methods allowing unprece-

dented intrusion into the privacies of life,

Americans are more

conscious of their privacy interests than ever and less confident that

those interests will be protected.

For all the valid criticisms that

may be levied against it, the Katz test, at the very least, offers an

avenue for confronting these concerns.

This is exactly what happened when the Court rendered its

decision in Carpenter v. United States, a landmark case extending

Fourth Amendment protection to historical cell site location

information (CSLI)—data generated, collected, and maintained by

cell phone service providers entirely outside the control of the

individuals the data describes.

Reactions to Carpenter varied,

but

it should be clear to anyone who understands the history and

context behind the Court’s decision that it represents a direct

repudiation of the notion that the appropriate Fourth Amendment

analysis is not “tied to measurement of the quality or quantity of

information obtained.”

In fact, the Carpenter analysis was

explicitly tied to both the quantity and quality of the information at

stake.

9. See Surveillance Technologies, ACLU, https://www.aclu.org/issues/privacy-technology/

surveillance-technologies [https://perma.cc/B7FW-S5HF].

10. Over 90 percent of American adults say that controlling what information is collected

about them and who collects it is important to them, but only 6 percent are “very confident”

that government agencies can keep their records private. Mary Madden & Lee Rainie,

Americans’ Attitudes About Privacy, Security and Surveillance, P

EW RSCH.CTR. (May 20,

2015), https://www.pewresearch.org/internet/2015/05/20/americans-attitudes-about-privacy-

security-and-surveillance/ [https://perma.cc/V2DD-FSXY].

11. 138 S. Ct. 2206 (2018).

12. Compare Vania Mia Chaker, Your Spying Smartphone: Individual Privacy Is

Narrowly Strengthened in Carpenter v. United States, the U.S. Supreme Court’s Most Recent

Fourth Amendment Ruling, 22

J. T

ECH.L.&POL’Y 1, 16 (2018) (arguing that the risk of

intrusive government surveillance “may militate in favor of strengthened judicial oversight”),

with Alan Z. Rozenshtein, Fourth Amendment Reasonableness After Carpenter, 128 Y

ALE

L.J.F. 943, 944, 950 (2019) (arguing that the categorical warrant requirement was a mistake,

and that Carpenter should be interpreted narrowly).

13. See Kyllo v. United States, 533 U.S. 27, 37 (2001).

14. See Carpenter, 138 S. Ct. at 2223 (deciding based on the “depth, breadth, and com-

prehensive reach” of CSLI).

1730 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

But the problem remains unaddressed, as the Court has yet to

outline an all-encompassing approach to Fourth Amendment cases

of unwarranted government surveillance that do not involve phys-

ical trespass.

These kinds of cases rarely overrule each other, so it

seems intuitive that the Court should be able to establish some

consistent through line. Yet, so far, it has not. This Note proposes

that it can be done, but only if the Court readily admits that the

Fourth Amendment no longer protects only property, but also infor-

mation. The ultimate outcome of Carpenter, and of every case that

has adequately applied the Katz test, has been to keep certain

information out of government hands.

Somewhat ironically, this includes Kyllo. It is from the language

of Kyllo, originally intended to protect the traditionally privileged

space of the home,

that this Note draws inspiration for its

proposed rule: absent probable cause, the Fourth Amendment

proscribes the government from obtaining information that could

not otherwise have been obtained without resorting to surveillance

technology or physically trespassing on private property. This

relatively simple standard, which can be called the obtainable infor-

mation rule, unifies the collective holdings of post-Katz surveillance

cases and provides a flexible framework for future decisions and

new technologies.

In order to understand exactly how the obtainable information

standard works, it is important to place it in the historical context

of Fourth Amendment doctrine. Part I of this Note will examine the

history of Fourth Amendment doctrine in cases of government

surveillance since 1967 and leading up to Carpenter v. United

States, a landmark case of critical importance to this argument.

Part II will explore some of the theories proposed by academics for

reconstructing, clarifying, or otherwise refining Fourth Amendment

surveillance doctrine in a palatable manner, and will explain why

each is unsatisfactory in at least one regard. It will then formally

15. Cases of government surveillance that do involve trespass are, of course, much easier

to resolve. It is widely accepted that the Fourth Amendment, at a minimum, prevents the

government from physically searching your home or interfering with your personal effects

without a warrant. See Kyllo, 533 U.S. at 31. This understanding is what allowed United

States v. Jones to be resolved unanimously, despite the Court’s deep divide over the issue of

GPS surveillance. See infra notes 53-59 and accompanying text.

16. See Kyllo, 533 U.S. at 34.

2021] THE QUALITATIVE FOURTH AMENDMENT 1731

propose the obtainable information standard as a satisfactory

alternative, capable of unifying post-Katz surveillance jurisprudence

under a single theory. Part III will discuss the intersection between

the obtainable information standard and third-party doctrine, which

has become a subject of much discussion (and concern) following

Carpenter. It will explain how the third-party doctrine need not be

thrown out the window in order to accommodate the proposed

standard.

Finally, it is worth noting that the purpose of this Note is not to

argue that the obtainable information rule is the solution most

resonant with the original meaning of the Fourth Amendment.

Rather, the primary purpose of the rule is to synthesize the various

holdings of the Supreme Court since Katz into a single, easy-to-

apply standard. As Part II will explain, there is also good reason to

believe that it is the most functionally desirable rule, but this Note

does not address the contention that any or all of the Supreme

Court’s holdings since Katz were themselves unconstitutional and

should be overruled.

HE RELEVANT HISTORY OF FOURTH AMENDMENT DOCTRINE

In the first half of the twentieth century, the Supreme Court had

consistently taken a physical property-based approach to assessing

Fourth Amendment claims.

Perhaps the most notable example of

this approach was Chief Justice Taft’s declaration in Olmstead v.

United States that the Fourth Amendment should be construed

narrowly enough to apply only to “material things—the person, the

house, his papers or his effects.”

The Taft Court ultimately held

that warrantless wiretapping did not violate the Fourth Amend-

ment, as there was no actual physical entry of the defendant’s house

or seizure of his belongings.

Following Olmstead, the Court con-

tinued to apply this narrow construction of the Fourth Amendment,

17. The Fourth Amendment protects “persons, houses, papers, and effects, against un-

reasonable searches and seizures.” U.S.

ONST. amend. IV.

18. 277 U.S. 438, 464 (1928).

19. Id. at 466.

1732 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

finding violations only when the government had physically in-

truded upon a defendant’s property.

A. Katz and the “Reasonable Expectation of Privacy”

Then, in 1967, the Court dramatically expanded the realm of

Fourth Amendment doctrine with its opinion in Katz v. United

States.

Charles Katz was convicted of transmitting wagering

information via telephone based on evidence gathered from war-

rantless FBI recordings of his phone conversations.

The district

and appeals courts quickly rejected his Fourth Amendment claims

because the agents never actually intruded on any property Katz

owned.

However, in a landmark decision, the Supreme Court

overruled Olmstead, rejecting the constitutional requirement of

physical trespass or seizure.

Moreover, the Court took a step

further and declared that “the Fourth Amendment protects people,

not places,”

effectively ending the era of the property-based

approach.

The majority opinion in Katz offered no clear standard for courts

to utilize when assessing Fourth Amendment claims, but Justice

Harlan’s concurring opinion proposed a two-step test: (1) that the

defendant exhibited a subjective expectation of privacy, and (2) that

the expectation is “one that society is prepared to recognize as

reasonable.”

Twelve years later, in Smith v. Maryland, a majority

of the Court adopted Harlan’s “reasonable expectation” test, and a

new era of Fourth Amendment jurisprudence was born.

All was not said and done, however. Katz’s new interpretation of

the rights protected against unreasonable search and seizure cre-

ated a slew of new questions, especially as technology continued to

20. See, e.g., Silverman v. United States, 365 U.S. 505, 510-12 (1961); Trevor Burrus &

James Knight, Katz Nipped and Katz Cradled: Carpenter and the Evolving Fourth

Amendment, 2018 C

ATO SUP.CT.REV. 79, 83.

21. 389 U.S. 347 (1967).

22. Id. at 353.

23. Id. at 348-49.

24. Id. at 353.

25. Id. at 351.

26. See Burrus & Knight, supra note 20, at 83.

27. Katz, 389 U.S. at 361 (Harlan, J., concurring) (internal quotation marks omitted).

28. 442 U.S. 735, 740 (1979).

2021] THE QUALITATIVE FOURTH AMENDMENT 1733

rapidly advance near the beginning of the twenty-first century.

Foreseeing the danger that advancing technology poses to sources

of constitutionally protected private activity, the Supreme Court

chose to sharpen the focus of Katz while simultaneously reintroduc-

ing a traditional spatial context to the analysis.

B. Ciraolo, Riley, and Public Exposure

A key qualification of the Court’s opinion in Katz was the idea of

public exposure: anything that has been “knowingly expose[d] to the

public” cannot reasonably be expected to be kept private.

This

would seem self-evident and perhaps more relevant to the first

prong of the Katz test. After all, if Charles Katz had shouted the

details of his criminal enterprise across a crowded room, he could

hardly have claimed any subjective expectation that his words

would remain private. However, the concept of “public exposure”

has taken up a more permanent home in the second prong of the

Katz test, which the Court has used to prevent unsuccessful at-

tempts to conceal criminal activity from creating constitutionally

protected interests.

This is exactly what happened in 1986, when the Court upheld

the conviction of Dante Ciraolo.

Law enforcement had been tipped

off that Ciraolo was growing marijuana in his yard but were unable

to confirm their suspicion from ground level due to the ten-foot fence

enclosing his property.

Without a search warrant, the police opted

instead to fly over Mr. Ciraolo’s property and surveil his yard from

a private airplane.

The officers identified multiple marijuana

plants and obtained a search warrant for that evidence.

The Supreme Court fully acknowledged Mr. Ciraolo’s subjective

expectation of privacy, exhibited by his efforts to conceal his yard

29. Andrew Guthrie Ferguson, The “Smart” Fourth Amendment, 102 CORNELL L. REV.

547, 588 (2017). For more on the context and reasoning behind the Kyllo decision, see

generally David A. Sklansky, Back to the Future: Kyllo, Katz, and Common Law, 72 M

ISS. L.J.

143 (2002).

30. Katz, 389 U.S. at 351.

31. California v. Ciraolo, 476 U.S. 207, 210 (1986).

32. Id. at 209.

33. Id.

34. Id.

1734 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

from prying eyes.

However, even an intent “to conceal assertedly

private activity” is meaningless in cases of public exposure.

According to the Court, the determinative fact was that any person

flying in publicly navigable airspace on a commercial flight or

private airplane could have “glanced down” and seen exactly the

same thing that the officers saw.

In other words, exposure to the

public is a hard line drawn when an effect or activity is located in a

space that could theoretically be observed from a public vantage

point, whether or not it actually was observed.

The Court affirmed as much in Florida v. Riley, a similar case

involving police use of a helicopter to surveil the interior of a dilap-

idated greenhouse from four hundred feet above.

The plurality

opinion upheld the conviction largely based on the fact that the

helicopter never left public airspace as defined by FAA regulations,

meaning any person in a helicopter could have lawfully made the

same observations.

Justice O’Connor’s concurring opinion was

hesitant to rely on such regulations, but would have instead in-

quired whether members of the public travel in helicopters at that

altitude “with sufficient regularity” so as to render any expectation

of privacy unreasonable.

In any case, Riley’s conviction was upheld

because the marijuana he was growing in his greenhouse had been

exposed to the public in the sense that any member of the public

could presumably have made such an observation without breaking

any laws or acting in an irregular manner.

Mr. Riley’s subjective

expectation that his greenhouse would remain private, and the fact

that no member of the public (other than police officers) subverted

that expectation, were found to be inconsequential.

What arose from these cases was a definitive limit on the scope

of the Katz test—and perhaps a necessary one given its potential

nebulousness. The Court effectively used the “public exposure”

35. Id. at 211.

36. Id. at 212 (internal quotation marks omitted) (quoting Oliver v. United States, 466

U.S. 170, 181-83 (1984)).

37. Id. at 213-14.

38. See 488 U.S. 445, 448 (1989).

39. Id. at 450-51.

40. Id. at 454 (O’Connor, J., concurring).

41. Id. at 450-51 (plurality opinion).

42. See id. at 451.

2021] THE QUALITATIVE FOURTH AMENDMENT 1735

exception to narrow Katz’s “reasonable expectation” prong so as to

apply only to effects and activity which had been kept completely

private from all potential public observation.

Along with the open

fields doctrine

and the third-party doctrine, which will be dis-

cussed later in this Note,

Ciraolo and Riley demonstrate the

Court’s willingness in the late 1980s to poke holes in personal expec-

tations of privacy using theoretical societal reasonableness.

C. Recent Cases Involving Modern Technology

By the dawn of the twenty-first century, it became clear that such

legal hole-poking posed a serious threat to traditional constitution-

ally protected spaces. In Kyllo v. United States, the Court considered

the warrantless use of a thermal imaging device to detect heat

signatures emanating from a suspect’s home.

The Court rejected

the government’s argument that these heat waves were not subject

to a reasonable expectation of privacy, finding instead that any

technology that obtained “information regarding the interior of the

home that could not otherwise have been obtained without physical

intrusion” constituted a search.

This line of reasoning allowed the

Court to emphasize the continued relevance of constitutionally

protected spaces under the Fourth Amendment (such as homes)

while simultaneously preserving the underlying Katz objective of

43. This principle is perhaps best illuminated by the Supreme Court’s 1984 decision in

Karo v. United States, 468 U.S. 705 (1984). In Karo, the Court held that the use of a

surreptitiously placed electronic tracking beeper to monitor the movement of a five-gallon can

of chemicals purchased by a suspected criminal violated the Fourth Amendment. Id. at 714.

What made this decision particularly remarkable was the Court’s decision in United States

v. Knotts only one year before, a case involving the use of a similar tracking beeper placed in

a can of chemicals, in which the Court held that there was not a Fourth Amendment violation.

460 U.S. 276, 285 (1983). The distinction, as explained by Justice White in the Karo majority

opinion, came down to the potential for simple “visual surveillance.” See Karo, 468 U.S. at

714. In Knotts, law enforcement had used the beeper to track the defendant along public

thoroughfares to the area where his cabin was located, activity that might just as well “have

been observed by the naked eye.” Id. at 713-14. In Karo, on the other hand, the beeper was

used to track movement within a private home, a place “not open to visual surveillance.” Id.

at 714.

44. See generally Oliver v. United States, 466 U.S. 170 (1984); United States v. Dunn, 480

U.S. 294 (1987).

45. See infra Part III.

46. 533 U.S. 27, 29-30 (2001).

47. Id. at 34 (internal quotation marks omitted).

1736 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

not “leav[ing] the homeowner at the mercy of advancing tech-

nology.”

Critically, the Court rejected the “proposition that

inference insulates a search”; that is, simply because the officers

had to infer additional conclusions from the heat data gathered did

not make the data any less private.

Justice Scalia’s majority opinion in Kyllo is plainly critical of the

Katz test, or at least of the way in which it is worded. Before even

attempting to apply it, Scalia uses the words “circular,” “subjective,”

and “unpredictable” to describe the “expectation of privacy that

society is prepared to recognize as reasonable.”

This problem

springs from the fact that, in Scalia’s opinion, the Fourth Amend-

ment “has never been tied to ... the quality or quantity of informa-

tion obtained.”

The government’s use of thermal imaging was

unconstitutional not because the actual activity observed was

private in nature but because activity that takes place within the

walls of the home is necessarily protected by the Fourth Amend-

ment.

In many ways, this can be seen as an attempt to refocus the

Court’s Fourth Amendment doctrine on specific constitutionally

protected areas—what might be called a property-based approach.

A decade after Kyllo, the Supreme Court ruled on another

landmark Fourth Amendment case, United States v. Jones.

Jones

argued that the government’s warrantless use of location data

gathered from a GPS device planted on his car constituted an

unreasonable search.

The Court ultimately ruled in favor of

Jones, although on admittedly mixed grounds.

Once again, Jus-

tice Scalia wrote the majority opinion, taking the traditional ap-

proach and arguing that the defendant’s rights were violated

when the officers “physically occupied private property for the

purposes of obtaining information.”

Justice Alito, joined by three

other Justices, concurred in the judgment but explicitly rejected

48. Id. at 35.

49. Id. at 36.

50. Id. at 34.

51. Id. at 37.

52. See id. at 34.

53. 565 U.S. 400 (2012).

54. Id. at 402-03.

55. See id. at 413.

56. Id. at 404.

2021] THE QUALITATIVE FOURTH AMENDMENT 1737

the majority’s pre-Katz approach.

Instead, Alito argued that the

long-term use of GPS monitoring to track a person’s precise move-

ment impinges on that person’s reasonable expectation of privacy.

Justice Sotomayor was the lone voice in agreement with both Scalia

and Alito.

As such, a five-member majority of the Court agreed

that the precise details of a person’s location over a period of time

are subject to a “reasonable expectation of privacy” and therefore de-

serving of Fourth Amendment protection.

The Court offered a more unified perspective in 2014 when it

considered the much-discussed case of Riley v. California.

The

issue in Riley was narrower than that in previous cases: merely the

ability of the government to search, without a warrant, data on a

cell phone recovered from a person during a lawful arrest.

However, the implications were no less important. The Court held

that, unlike other objects that might be kept on an arrestee’s person,

“[c]ell phones differ in both a quantitative and a qualitative sense.”

Unlike a wallet or paper document, modern cell phones can hold

vast quantities of personal images, private communications, and

personal information that “is not physically limited in the same

way.”

The Court reasoned that to allow unwarranted searches of

such information would be to allow unreasonable government

intrusion into “the privacies of life.”

Interestingly, the majority

made no mention of Katz in its opinion, despite the clear connection.

D. Carpenter v. United States in Context

Carpenter, therefore, was only the most recent in a long line of

cases since Katz cyclically broadening and refining the scope of

57. Id. at 426 (Alito, J., concurring) (“[T]he Court’s reliance on the law of trespass will

present particularly vexing problems in cases involving surveillance that is carried out by

making electronic, as opposed to physical, contact with the item to be tracked.”).

58. Id. at 430.

59. See id. at 414 (Sotomayor, J., concurring) (“When the government physically invades

personal property to gather information, a search occurs.... Nonetheless, as Justice Alito

notes, physical intrusion is now unnecessary to many forms of surveillance.”).

60. 573 U.S. 373 (2014).

61. See id. at 378.

62. Id. at 393.

63. Id. at 394.

64. Id. at 403 (quoting Boyd v. United States, 116 U.S. 616, 630 (1886)).

1738 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

Fourth Amendment protection; it was against this background

that the Court rendered its decision. And while some scholars

heralded the Court’s holding in Carpenter as revolutionary,

others

wondered why it took the Court so long.

Whatever the case, it

should be noted that the key concerns about the government’s

access to private information, made possible by technological

advances discussed in Jones and Riley v. California, underpin the

outcome of Carpenter.

The same could be said about the technolog-

ical equivalence principle adopted in Kyllo.

This makes Carpenter

the latest installment in a trilogy (or perhaps a tetralogy?) of

decisions confronting the interplay between the Fourth Amendment

and continuously advancing surveillance technology.

For these

reasons, it is important to keep context in mind when considering

Carpenter.

1. The Facts of the Case

Over a period of four months in 2011, a group of armed men

robbed a series of Radio Shack and T-Mobile stores in Detroit.

Police officers arrested four men in connection with the robberies,

one of whom admitted to participating in the crime spree and pro-

vided the names and phone numbers of fifteen accomplices.

Using

this information, prosecutors procured court orders under the

Stored Communications Act compelling two wireless carriers to dis-

close cell site location information (CSLI) data for several suspects,

including Timothy Carpenter.

65. See, e.g., Paul Ohm, The Many Revolutions of Carpenter, 32 HARV. J.L. & TECH. 357,

358 (2019) (“Carpenter works a series of revolutions in Fourth Amendment law.”).

66. See, e.g., Susan Freiwald & Stephen Wm. Smith, The Carpenter Chronicle: A Near-

Perfect Surveillance, 132 H

ARV.L.REV. 205, 231-32 (2018) (arguing that “it is sobering to

consider” how long it took the Court to correct “a widespread error that enabled constitutional

violations on an epic scale”).

67. Chaker, supra note 12, at 7-8.

68. See Ohm, supra note 65, at 394-95.

69. See Freiwald & Smith, supra note 66, at 216.

70. Carpenter v. United States, 138 S. Ct. 2206, 2212 (2018).

71. Id.

72. Id.

2021] THE QUALITATIVE FOURTH AMENDMENT 1739

CSLI is, in essence, all the information that cell phones relay to

the nearby cell towers.

Wireless carriers routinely store customers’

historical CSLI, which can triangulate a cell phone’s location at any

given time.

The Stored Communications Act, originally enacted in

1986 as Title II of the Electronic Communications Privacy Act, per-

mits disclosure of such data upon a showing of “reasonable grounds

to believe” that it is “relevant and material to an ongoing criminal

investigation.”

Of course, this standard is notably lower than that

required to obtain a warrant, which requires probable cause.

Altogether, the government procured 12,898 location points cat-

aloguing Carpenter’s movements over a period of four months.

Before trial, Carpenter moved to suppress the CSLI, but the district

court denied his motion.

At trial, the government used the CSLI

to place Carpenter’s phone near four of the robberies.

Based

largely on this evidence, Carpenter was convicted of all but one of

the charges and sentenced to more than one hundred years in pris-

on.

The Sixth Circuit Court of Appeals affirmed the conviction, and

the United States Supreme Court granted certiorari to resolve a

circuit court split on the issue.

2. The Court’s Holding

The opinion of the Court, authored by Chief Justice Roberts,

began its analysis by reaffirming the Court’s commitment to up-

holding the “reasonable expectation of privacy” standard adopted in

Katz.

However, the Court chose to go more in-depth by using a

multifactor analysis which, although not explicitly listed in the

73. Stephanie Lacambra, Cell Phone Location Tracking or CSLI: A Guide for Criminal

Defense Attorneys, E

LEC.FRONTIER FOUND. (Oct. 30, 2017), https://www.eff.org/files/2017/10/

30/cell_phone_location_information_one_pager_0.pdf [https://perma.cc/M2MD-R6D6].

74. Id.

75. 18 U.S.C. § 2703(d).

76. Carpenter, 138 S. Ct. at 2221.

77. Id. at 2212.

78. Id.

79. Id. at 2212-13.

80. Id. at 2213.

81. Id.

82. See id.

1740 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

opinion, was central to the holding.

While each of these factors,

including duration, scope, and intrusiveness, informed the Court’s

ultimate decision, none were dispositive on their own.

It was, at its

heart, a balancing test—much to the chagrin of the dissenters.

In sum, the Court found that by acquiring his CSLI, the govern-

ment impinged Carpenter’s reasonable expectation of privacy and

therefore committed a search under the meaning of the Fourth

Amendment.

Katz and Jones taken together, according to the

Court, stood for the proposition that people can maintain a reason-

able expectation of privacy in their activities even when those

activities are performed outside the sanctuary of their home.

Likewise, Riley v. California and Kyllo addressed the need for

Fourth Amendment doctrine to grow and change in proportion to

the changing nature of technology.

Therefore, even an interpreta-

tion of the Constitution that demanded “preservation of that degree

of privacy against government that existed when the Fourth

Amendment was adopted” requires a somewhat flexible approach.

The Court cited the five-Justice majority in Jones for the propo-

sition that society fully expects that law enforcement agents would

not or could not “catalogue every single movement of an individu-

al[ ],” suggesting that to allow the government access to CSLI would

contravene that decision.

After all, taken together, Carpenter’s

CSLI provided “an all-encompassing record of ” his location and

movement over a long period.

The Court seized on both the sen-

sitive nature of the CSLI and the fact that it provided “near perfect

surveillance,” far removed from the abilities of a constable on foot

or other eighteenth-century equivalent.

After finding a search under the Fourth Amendment, the Court

quickly affirmed the general presumption that warrants or warrant

83. Freiwald & Smith, supra note 66, at 219.

84. See id. at 219-21; Carpenter, 138 S. Ct. at 2213-14 (“[N]o single rubric definitively

resolves which expectations of privacy are entitled to protection.”).

85. See Carpenter, 138 S. Ct. at 2231-32 (Kennedy, J., dissenting).

86. Id. at 2223 (majority opinion).

87. Id. at 2217.

88. See id. at 2218-19.

89. Id. at 2214 (quoting Kyllo v. United States, 533 U.S. 27, 34 (2001)).

90. Id. at 2217; see also supra notes 53-59 and accompanying text.

91. Carpenter, 138 S. Ct. at 2217.

92. Id. at 2218; see also Freiwald & Smith, supra note 66, at 221.

2021] THE QUALITATIVE FOURTH AMENDMENT 1741

exceptions are required for Fourth Amendment searches.

Thus, a

revolution in Fourth Amendment doctrine was born.

Or so it would

seem.

Though the Carpenter decision may appear unprecedented at first

glance,

it actually marks a perfectly logical and predictable de-

velopment in Fourth Amendment doctrine. In fact, the Supreme

Court’s entire post-Katz nontrespassory surveillance jurisprudence,

as jumbled as it may seem, could very well be reduced to a few non-

conflicting principles. Katz introduced the principle that expecta-

tions of privacy are more important than physical spaces. Ciraolo,

Riley, Karo, and other cases from the 1980s defined the limit of

these expectations, drawing the line at potential public exposure.

Kyllo, Jones, and other cases from this century have demonstrated

that advancing technology does not lower the bar for public

exposure. As Part II will discuss, in the correct context, a path can

be traced through these cases that leads right to Carpenter and

gives us a roadmap for the future.

II.

INDING A THROUGH LINE IN FOURTH AMENDMENT DOCTRINE

It would seem important to find a consistent direction taken by

the Supreme Court on Fourth Amendment surveillance issues, espe-

cially given that major government surveillance cases since Katz

have avoided overruling each other.

However, the only explicitly

enumerated holding common to all these cases is the “reasonable

expectation of privacy,” a guideline which is, at best, “circular” and

“subjective.”

For the purposes of this discussion, it is important to distinguish

between traditional searches or seizures and government surveil-

lance, which only became a Fourth Amendment issue after Katz.

The dismissal of the traditional property-based approach was nec-

essary in Katz to account for nontrespassory surveillance, which can

93. Carpenter, 138 S. Ct. at 2221.

94. Ohm, supra note 65, at 358.

95. The dissenters certainly thought so. See Carpenter, 138 S. Ct. at 2230 (Kennedy, J.,

dissenting).

96. See supra Part I.

97. See Kyllo v. United States, 533 U.S. 27, 34 (2001).

1742 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

be just as violative of a person’s privacy as physical searches.

Government entry into constitutionally protected spaces or seizure

of personal effects without a warrant or probable cause has always

been considered violative of the Fourth Amendment.

The major

Supreme Court cases since Katz listed above deal almost exclusively

with nontrespassory surveillance, which should be the primary

focus of any modern Fourth Amendment theory, and is therefore the

focus of this Note.

A. The Many Unsatisfactory Candidates

Many potential candidates for an all-encompassing theory of

Fourth Amendment rights claim to effectively unify the post-Katz

doctrine. Some have been explicitly proposed, while others are

implicit in the Court’s opinions. However, most leave unsatisfactory

holes in the doctrine or else fail to account for all the Court’s prior

decisions. Ideally, a unifying theory would include and account for

every currently in-force Supreme Court decision without necessitat-

ing that any of them be overruled.

Using Carpenter and Kyllo as a lens, it might be tempting to defer

to the Court’s historical prerogative to preserve “that degree of

privacy against government that existed when the Fourth Amend-

ment was adopted.”

100

This approach has some appeal, especially

because the holding of Kyllo was, at least in part, motivated by the

fact that when the Bill of Rights was adopted, only physical trespass

would have allowed the same level of observation of activity inside

the home as a thermal sensor does today.

101

Similarly, as Chief Jus-

tice Roberts pointed out in Carpenter, no individual investigator or

team of investigators could possibly hope to gather such extensive

location information as was provided by CSLI, a very recent tech-

nological development.

102

Using the “at the time the Fourth Amend-

ment was adopted” standard would certainly go above and beyond

98. See Katz v. United States, 389 U.S. 347, 353 (1967).

99. See, e.g., Boyd v. United States, 116 U.S. 616, 621 (1886).

100. Carpenter, 138 S. Ct. at 2214 (quoting Kyllo, 533 U.S. at 34).

101. See Kyllo, 533 U.S. at 34.

102. See Carpenter, 138 S. Ct. at 2218.

2021] THE QUALITATIVE FOURTH AMENDMENT 1743

the call for protecting individuals from the threat of modern sur-

veillance technology encroaching on private life.

But such an approach does not square with the Court’s decisions

in Ciraolo or Florida v. Riley—or even, quite frankly, the Katz test.

Airplanes and helicopters were certainly not around at the time the

Framers adopted the Fourth Amendment. One could easily conclude

that aerial surveillance of any kind exceeds the degree of privacy

that existed when the Fourth Amendment was adopted. Had Mr.

Ciraolo constructed his ten-foot perimeter fence in 1791, he would

have effectively ensured that the contents of his yard would remain

private—and could reasonably have expected so.

103

It seems, then,

that the historical standard is less of a bright-line rule and more of

a general expression of society’s expectations of privacy. The Court

in Carpenter admitted as much, using “historical understandings”

only to “inform[ ]” the analysis which has “no single rubric.”

104

essence, the historical standard is just a rewording of what “society

is prepared to recognize as reasonable”

105

and therefore no less

circular.

Another approach might be to refocus on the “knowingly ex-

pose[d]” language from Katz,

106

as the Court did in Ciraolo and

Florida v. Riley.

107

The language from those opinions seems to sug-

gest that this was indeed the direction the Rehnquist Court hoped

to push Fourth Amendment jurisprudence.

108

It would be a rela-

tively simple rule that could (at least theoretically) refine the Katz

test without abandoning it. What has been knowingly exposed to

observation from any public vantage point is necessarily not subject

to a reasonable expectation of privacy. Rather than threaten the

holding of Katz, such a rule would merely take the guesswork out of

the second prong. Furthermore, it would imply that activity which

has not been exposed to the public, such as activity within the walls

103. See California v. Ciraolo, 476 U.S. 207, 209 (1986).

104. Carpenter, 138 S. Ct. at 2213-14 (citing Carroll v. United States, 67 U.S. 132, 149

(1925)).

105. See Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring) (internal

quotation marks omitted).

106. See id. at 351.

107. See Ciraolo, 476 U.S. at 213; Florida v. Riley, 488 U.S. 445, 449 (1989).

108. See Riley, 488 U.S. at 449 (“As a general proposition, the police may see what may be

seen ‘from a public vantage point where [they have] a right to be.’” (alteration in original)

(quoting Ciraolo, 476 U.S. at 213)).

1744 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

of the home or documented on a personal cell phone, would be

protected by the Fourth Amendment, complying with the Court’s

later holdings in Kyllo and Riley v. California.

However, such a rule is plainly not conducive to the holdings in

Jones or Carpenter. The legal challenges posed by location-tracking

technology are relatively new, but they are no less indicative of

Fourth Amendment concerns.

109

Unwarranted CSLI and GPS track-

ing data represent a “seismic shift[ ]”

110

in surveillance technology

that allows the government to intrude on the “privacies of life”

111

ways never before imagined. Surely, Mr. Carpenter’s movements

over those four months were exposed to the public in the sense that

they took place in public spaces where he could have been observed

by anyone who happened to be there.

112

Had there been a police

officer present at any one of the robberies, or all four, who had seen

Mr. Carpenter and positively identified him, this information would

certainly not be protected by the Fourth Amendment. Rather,

something about the sum total of the information makes it constitu-

tionally protected, regardless of the fact that all of the activity in

both Jones and Carpenter was technically exposed to public view.

Of course, yet another proposal is to return to a property-centric

interpretation of the Fourth Amendment. This has drawn support

from certain academic writers, such as Trevor Burrus and James

Knight, who believe that clearer jurisprudence based on property

law can help untangle the confusing legacy of the Katz test.

113

The

idea is that the kinds of property protected by the Fourth Amend-

ment can be expanded into areas such as CSLI without resorting to

nebulous and highly subjective interpretations of reasonableness.

114

While continuing to allow the government to carry out naked-eye

surveillance without trespassing, this approach can still be said to

square with Kyllo and Riley v. California, because the interior of the

home or personal cell phone is included in those “constitutionally

protected area[s]” necessarily subject to a legitimate expectation of

109. See Carpenter, 138 S. Ct. at 2223.

110. Id. at 2219.

111. Id. at 2217 (quoting Riley v. California, 573 U.S. 373, 403 (2014)).

112. See id. (“A person does not surrender all Fourth Amendment protection by venturing

into the public sphere.”).

113. See Burrus & Knight, supra note 20, at 110-11.

114. See id.

2021] THE QUALITATIVE FOURTH AMENDMENT 1745

privacy.

115

It would certainly fit right in with Justice Scalia’s ad-

monition that Fourth Amendment analysis does not turn on the

nature of the information gathered.

116

In fact, the property-based

approach could be construed to include all the Court’s post-Katz

decisions, so long as the definition of property is loose enough to

include intellectual property and the like.

However, something about the property-based approach does not

conform with the spirit of the Fourth Amendment, or at least not

how it has been construed in the past half-century. One might very

well suggest that the determinative issue in Carpenter was the

property at stake—namely the CSLI data itself.

117

But from Mr.

Carpenter’s perspective, and seemingly the Court’s perspective as

well, that was not the case.

118

After all, Carpenter had no interest

in the physical data itself; it would be hard to imagine any individ-

ual claiming actual ownership over the ones and zeros that make up

CSLI. Rather, what infringed upon his expectation of privacy were

the inferences drawn from the data.

119

Mr. Carpenter likely had no

knowledge that this data existed before it was used to convict him,

and he almost certainly would have preferred that it never existed

at all. Therefore, it can hardly be said that he had a traditional

property interest in the CSLI. His interest was rooted in keeping

the government from inferring (via CSLI or otherwise) the details

of his location over an extended period.

120

This is not property, it is

information.

The crux of the issue is that CSLI falls so far outside the common

understanding of “property” that it threatens to render the term

meaningless. CSLI is created, managed, and controlled by cell phone

service providers, not individual customers.

121

In order to fit Car-

penter within the scope of the property-based approach, one would

have to argue that individuals have a legitimate property interest

in any data that describes them or their activities, regardless of

115. See Kyllo v. United States, 533 U.S. 27, 34 (2001) (quoting Silverman v. United States,

365 U.S. 505, 512 (1961)).

116. See id. at 37.

117. See Carpenter, 138 S. Ct. at 2211-12.

118. See id. at 2218-19.

119. See id.

120. See id.

121. See id. at 2211-12.

1746 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

whether they had a hand in creating or managing it. This is, of

course, an unreasonable rule. For instance, an individual cannot

possibly be said to have a property interest in another’s diary entry

that describes her or in a newspaper article that discusses her ac-

tivities. She may have a privacy interest in these sources, but it is

a privacy interest that is separate and distinct from any legitimate

property interest.

The oft-repeated holding in Katz that “the Fourth Amendment

protects people, not places”

122

is indicative of the notion that the

Court’s post-1967 jurisprudence has really protected information

and knowledge at least as much, if not more so, than property. The

facts of Katz reflect this. It was not the location from which Mr.

Katz was making a phone call that was protected by the Constitu-

tion, much less whatever physical properties a phone call can be

said to exhibit.

123

What was protected was the content of the con-

versation, that is, information.

124

Even in Kyllo, the very case in which Justice Scalia declared

“quality or quantity of information” irrelevant to the Fourth Amend-

ment analysis,

125

it was information being protected rather than

property. The Kyllo Court’s holding that activity and effects within

the home are necessarily subject to Fourth Amendment protection

simply generalizes a category of information that is protected.

126

Contrary to Justice Scalia’s characterization of the issue, the fact

that the activity in Kyllo took place on a traditionally protected

property was only a precondition for determining the quality of the

information at stake.

127

The effective outcome of Kyllo is that activ-

ities and effects within certain spatial contexts (namely, the home)

have been determined to exhibit the quality of constitutionally

protected private activity, regardless of what that activity actually

is.

122. Katz v. United States, 389 U.S. 347, 351 (1967).

123. See id. at 354.

124. See id.

125. See Kyllo v. United States, 533 U.S. 27, 37 (2001).

126. See id. at 34.

127. See id.

2021] THE QUALITATIVE FOURTH AMENDMENT 1747

Similarly, in Carpenter, it was both the quantity and quality of

the information at stake that led the Court to its decision.

128

This

reality is not lost on academic commentators

129

and certainly was

not lost on the dissenting Justices.

130

Although a property-based

approach might be shaped and squeezed into the mold of post-Katz

Fourth Amendment doctrine, it does not address the heart of the

issue, and it certainly does not account for the direction that the

Court seems to be headed.

B. An Effective Information-Based Approach

Given the case law discussed above,

131

the most appropriate all-

encompassing Fourth Amendment theory in cases of warrantless

government surveillance would take into account the private nature

of certain kinds of information, without barring the government

from observing or learning what any member of the public already

lawfully could observe or learn (that is, what has been publicly

exposed

132

). Such a theory would look something like this: absent

probable cause, the government is barred from obtaining any in-

formation that could not otherwise be obtained without resorting

to surveillance technology or trespassing. Such a rule is relatively

simple, accounts for all post-Katz holdings, and provides a work-

able roadmap for future decisions.

1. The Obtainable Information Approach as a Through Line

for Post-Katz Fourth Amendment Cases

It is easy to see how this proposed standard would encompass the

holdings of Carpenter and Jones, given the “comprehensive reach”

of the information at issue in those cases.

133

As pointed out by Chief

128. See Carpenter v. United States, 138 S. Ct. 2206, 2223 (2018) (deciding based on the

“depth, breadth, and comprehensive reach” of CSLI).

129. See, e.g., Evan Caminker, Location Tracking and Digital Data: Can Carpenter Build

a Stable Privacy Doctrine?, 2018 S

UP.CT.REV. 411, 445-46.

130. See Carpenter, 138 S. Ct. at 2224 (Kennedy, J., dissenting) (“[T]he Court [has] un-

hing[ed] Fourth Amendment doctrine from the property-based concepts that have long

grounded [it].”).

131. See supra Part I.

132. See Katz v. United States, 389 U.S. 347, 351 (1967).

133. See Carpenter, 138 S. Ct. at 2223.

1748 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

Justice Roberts, no individual person could possibly hope to compile

an exhaustive account of a suspect’s every movement over a period

of multiple days, let alone several months.

134

Therefore, it is not the

public exposure of the activity generally that matters but instead

the public availability of the cumulative weight of the information,

and the inferences drawn therefrom. The information at issue in

Carpenter, as revealed by the CSLI, was only available to the gov-

ernment by using the CSLI technology itself, or some similar

location tracking technology.

135

There is simply no way that such a

vast quantity of information could be obtained otherwise. As such,

it violates the rule and should be held unconstitutional. Although

the Jones Court ultimately ruled on physical trespass grounds,

136

the same principles can apply to the location data in that case.

Moreover, a five-Justice majority would have ruled in favor of Jones

even if the police had not trespassed.

Riley v. California too fits nicely into the obtainable information

standard. It can hardly be said that the personal information kept

on a cell phone is available to anyone who does not either hack into

the phone electronically or physically seize the phone itself.

137

As discussed earlier, the Kyllo holding is essentially a quality-

based analysis of information in certain spatial contexts.

138

In any

case, a plain application of the obtainable information standard

would yield the same result, and for largely the same reasons.

139

Information gathered from observing activity hidden within the

walls of a private home is inaccessible, except by trespassing or

using surveillance technology. That is, after all, exactly what hap-

pened in Kyllo.

140

Shifting the focus of the analysis from the location

to the type of information at stake does not change the outcome but

refines it. The information in Kyllo, as is the case with all infor-

mation about activity and effects within the walls of a home, should

134. Id. at 2218.

135. See id.

136. See United States v. Jones, 565 U.S. 400, 404-05 (2012).

137. See generally Riley v. California, 573 U.S. 373 (2014).

138. See supra notes 125-26 and accompanying text.

139. It was, in fact, the language and reasoning of the Kyllo holding that served as

inspiration for the obtainable information standard. See Kyllo v. United States, 533 U.S. 27,

34 (2001).

140. See id. at 29-30.

2021] THE QUALITATIVE FOURTH AMENDMENT 1749

be protected from the government precisely because the spatial

context prevents all nonsurveillance and nontrespass methods of

obtaining it.

Moving further back in the Fourth Amendment timeline, Ciraolo

and Florida v. Riley easily fall within the obtainable information

standard as well. Those decisions hinged on the fact that a person

occupying public airspace—whether or not they were trying to

surveil the defendant’s property—could see anything and everything

the officers themselves saw.

141

Neither surveillance technology nor

trespass was required to observe the marijuana growing in Mr.

Ciraolo’s yard or Mr. Riley’s greenhouse, only an airplane or

helicopter.

142

Therefore, the information at stake, namely that the

defendants were growing marijuana in those locations, was ob-

tainable without breaking the rules of the obtainable information

standard. Such observation would therefore be held constitutional,

consistent with the Court’s opinions.

The beauty of the obtainable information standard is that it gets

to the heart of the reasonable expectation of privacy test as laid out

by Justice Harlan,

143

without compromising any of the values or

policy concerns enumerated by the Court since Katz. The spirit of

the two-pronged test is the preservation of private information, and

the direction of the Court since adopting the test is best encapsu-

lated by preventing the government from obtaining information

otherwise unobtainable without resorting to surveillance technology

or physical trespass.

2. The Information-Based Approach as a Roadmap for the

Future

As technology continues to advance, the threats it poses to per-

sonal privacy will no doubt grow as well. One major problem with

the property-based or public exposure standards is that they gener-

ally fail to account for the “seismic shifts” in technology that allow

141. See California v. Ciraolo, 476 U.S. 207, 213-14 (1986); Florida v. Riley, 488 U.S. 445,

451-52 (1989).

142. See Ciraolo, 476 U.S. at 213-14; Riley, 488 U.S. at 451-52.

143. See Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring).

1750 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

the government to peer into formerly private areas of life.

144

The

Court’s Fourth Amendment theory should account for such shifts by

preventing the government from using them to unduly intrude into

private life. At the same time, the Court should not overly burden

the government by preventing police from obtaining information

that is accessible via the use of common modern technology that

serves nonsurveillance purposes.

a. The Continuing Relevance of the Trespass Qualification

This Note certainly does not argue that property interests play no

part in Fourth Amendment surveillance cases. Scalia’s contention

in Kyllo that the interior of a home is necessarily protected by the

Fourth Amendment is not wrong, it merely misrepresents why that

protection is necessary.

145

Activities and effects that are placed

within the walls of a house are not magically transformed into the

privacies of life merely by virtue of being there. They are protected

because we expect them to be protected. There is nothing special

about the interior of a house per se, except that the owner of the

house exercises control over who may enter it and therefore ex-

ercises de facto control over the flow of information from within.

As such, it is appropriate to keep the “trespass” qualification from

Kyllo attached to the obtainable information standard. In other

words, if the only way information can be obtained is by trespassing

on private property, then that information is protected by the

Fourth Amendment. This is a sound principle, but it is incomplete.

It does not account for the threat of advanced surveillance technol-

ogy which does not require any such trespass.

b. Defining “Surveillance Technology”

As already noted, the obtainable information standard would ef-

fectively prevent the government from using surveillance technology

to obtain information that could not otherwise have been obtain-

ed.

146

This would account for any future technological developments

144. See Carpenter v. United States, 138 S. Ct. 2206, 2219 (2018).

145. See supra notes 125-26 and accompanying text.

146. See supra Part II.B.1.

2021] THE QUALITATIVE FOURTH AMENDMENT 1751

providing access to information that was not already exposed in

some way. Likewise, the enumerated concerns of the Carpenter

Court would be readily addressed.

147

The only potential hurdle for

future courts to consider would be the legal definition of “sur-

veillance technology.”

This determination could likely be made on a case-by-case basis

without much trouble, but a recommended starting place should be

as follows: surveillance technology is any technology used to acquire

information that could not casually be acquired. As general as this

may seem, it provides an important distinction, so far as the case

law discussed in this Note is concerned.

Consider the airplane and helicopter at issue in Ciraolo and

Florida v. Riley, respectively.

148

In each of those cases, the Court

relied on the fact that any person in an aerial vehicle occupying

public airspace could have observed the illegal activity, regardless

of whether they were trying to surveil the property below them.

149

A passenger on a commercial flight that happened to be passing

overhead could easily have “glanced down” and seen everything the

police did.

150

As such, the information at stake in Ciraolo and

Florida v. Riley, namely that the defendants were growing mari-

juana on their property, could have been casually acquired.

151

That

law enforcement used this technology specifically for the purpose of

surveillance is irrelevant. What matters is that the information

gathered was not otherwise unobtainable.

On the other hand, technology such as the thermal sensor used in

Kyllo would clearly fall under the definition of “surveillance tech-

nology.”

152

Information about the interior of a house is unobtainable

without trespassing into the home or using some kind of sense-

enhancing technology.

153

Likewise, such information cannot be ca-

sually acquired in the same way as information about the contents

of a fenced-in yard. Another way to think about this distinction is

147. See Carpenter, 138 S. Ct. at 2219.

148. See California v. Ciraolo, 476 U.S. 207, 209 (1986); Florida v. Riley, 488 U.S. 445, 448

(1989).

149. See Ciraolo, 476 U.S. at 213-14; Riley, 488 U.S. at 450-51.

150. See Ciraolo, 476 U.S. at 213-14.

151. See id. at 209; Riley, 488 U.S. at 448.

152. See Kyllo v. United States, 533 U.S. 27, 29-30 (2001).

153. See id. at 34.

1752 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

to consider whether a person could acquire the information at issue

without actively trying to do so. Using a thermal imaging device, or

any other device capable of penetrating the walls of Kyllo’s home,

would necessarily require an active intent. It would be absurd to

propose that any person might have “glanced” into a thermal

imaging device aimed at Kyllo’s house and seen everything the

police had seen without meaning to see what was inside his house.

One key aspect of this definition of “surveillance technology” is

that it hinges on the nature of the information, as well as the nature

of the technology. Any legal definition of “surveillance technology”

that rests only on the nature of the technology itself would lead to

undesirable outcomes. For example, most people would likely agree

that a high-resolution camera mounted on a government satellite

used to monitor individuals is a “surveillance technology” by its own

standards. But what if such a satellite were used to photograph a

suspect who walked through a public park in the middle of the day?

Regardless of the nature of the technology used to take the photo-

graphs, it would be at odds with the Supreme Court’s post-Katz

jurisprudence to say that the suspect had any legitimate privacy

interest in the fact that he was in that particular public place on

that particular day. Any person (or law enforcement officer) who

happened to be in the park that day could have seen him without

actively trying to monitor his whereabouts. In other words, the

information could have been casually acquired.

In a sense, the Supreme Court has already drawn this distinction

with its dual holdings in Knotts and Karo, two cases that involved

the use of nearly identical electronic tracking beepers to monitor a

suspect’s movement.

154

Although the Court expressed its opinion in

Karo through the language of traditional property protection, the

critical difference between these two cases was that the beeper in

Knotts was used only to track movement through public thorough-

fares.

155

In Karo, the beeper was used to track movement within a

private residence.

156

As such, the information at stake in Knotts

could have been easily acquired by any officer who tailed the defen-

dant on that day, whereas the information in Karo could only have

154. See supra note 43.

155. See United States v. Knotts, 460 U.S. 276, 281 (1983).

156. United States v. Karo, 468 U.S. 705, 714 (1984).

2021] THE QUALITATIVE FOURTH AMENDMENT 1753

been acquired by trespassing had it not been for the use of the

beeper technology. The Knotts/Karo distinction is a good example

of how the exact same technology can satisfy the proposed definition

of “surveillance technology” in some cases but not in others, depend-

ing on the nature of the information it has been used to acquire.

Notably, such a definition would be ambiguous when applied to

simple quasi-surveillance equipment such as binoculars. A strong

case could be made that activity that is observable only using

binoculars or similar visual-enhancement technologies cannot be

casually acquired. However, people frequently use binoculars for

purposes other than surveillance. The resolution to such a case

would rest on a factual determination of the likelihood that a

person, using some manner of simple visual-enhancement technol-

ogy for a purpose other than surveillance of the activity or property

in question, could have obtained the information at issue casually,

without active intent.

This ambiguity is intentional, as society’s general expectation of

privacy concerning such surveillance is unclear. Any definition of

“surveillance technology” as the phrase is used in the obtainable

information standard would need to be flexible, so as to align with

the public’s changing understanding of what can reasonably be

expected to remain private. In any case, the legal definition pro-

posed above would become an issue only in the narrow set of cases

in which the government surveilled an individual and gathered

information that could only have been acquired casually using some

form of common quasi-surveillance sense-enhancing technology in

a nonsurveillance manner. No such case has yet presented itself to

the Supreme Court.

III.

HE THORNY THIRD-PARTY DOCTRINE

After the Katz decision shifted the focus of Fourth Amendment

inquiries away from physical property,

157

a paradox of sorts arose

when it came to the legal interpretation of what one could reason-

ably expect to keep private. If Fourth Amendment searches were no

longer tied to physical spaces the defendant occupies or owns, then

157. See supra notes 21-28 and accompanying text.

1754 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

could a defendant claim a “reasonable expectation of privacy”

regarding objects or information in the possession of another

person? From a law enforcement perspective, this would be prob-

lematic: it would allow criminals to use third-party services to

commit crimes without exposing themselves to the public spaces

open to government surveillance.

158

The Court’s solution to this

conundrum was simply to make such an outlet wholly unavailable.

In other words, “[u]sing a third party [will] not change the overall

level of Fourth Amendment protection.”

159

This standard came into

being through a fusion of two cases wrestling with the application

of Katz in the 1970s and would come to be known as the Smith-

Miller standard.

A. The Smith-Miller Standard

In 1973, agents from the Alcohol, Tobacco, and Firearms Bureau

(ATF) presented subpoenas to the presidents of two Georgia banks

at which Mitch Miller held personal accounts.

160

The subpoenas

compelled the release of all bank statements and other financial

records related to Miller’s accounts in their possession.

161

The banks

complied with the subpoenas, and the recovered financial informa-

tion revealed—as the agents had suspected—a number of financial

transactions related to the illegal practice of possessing a still and

distilling whiskey without paying the appropriate taxes.

162

The

subpoenas had not been issued by a court, and Miller had not been

informed that the subpoenas had been served.

163

His motion to

suppress the evidence was denied by the district court, but his sub-

sequent conviction was reversed by the court of appeals on Fourth

Amendment grounds.

164

The Supreme Court was thus faced with the

158. See Orin S. Kerr, The Case for the Third-Party Doctrine, 107 MICH.L.REV. 561, 575

(2009).

159. Id. at 577.

160. United States v. Miller, 425 U.S. 435, 437 (1976).

161. Id.

162. See id. at 436, 438.

163. Id. at 438-39.

164. Id.

2021] THE QUALITATIVE FOURTH AMENDMENT 1755

question of whether the financial records at issue were subject to a

“reasonable expectation of privacy.”

165

The Court concluded that the answer to that question must be

“no.”

166

The Court pointed out that Miller “can assert neither owner-

ship nor possession” over “the business records of the banks.”

167

The

Court rejected Miller’s contention that he justifiably relied on the

continued privacy of his financial information, even after turning it

over to the banks.

168

Invoking Katz, the Court held that Miller had

“knowingly expose[d] to the public” his financial information, setting

it outside the scope of Fourth Amendment protection.

169

The Court

refused to accept the proposition that Miller could retain any

reasonable expectation of privacy over information that he had

voluntarily exposed to the public.

170

The Court considered a similar case, Smith v. Maryland, in 1979,

when a telephone company installed a pen register at the request of

the police to record the numbers dialed from the home of a sus-

pected criminal.

171

The register revealed that the suspect had placed

a call to the phone of a robbery victim who had been receiving

threatening calls from a person identifying himself as the robber.

172

Based on this evidence, the suspect was charged and convicted of

robbery, over his attempted motion to suppress.

173

Even though this case bears substantial similarities to the facts

of Katz, the Court still found grounds for distinction. Unlike the

contents of a telephone conversation, which the Katz Court had

unequivocally placed under the protection of the Fourth Amend-

ment, a pen register records only the number that an individual has

165. See id. at 442.

166. Id.

167. Id. at 440.

168. Id. at 442.

169. Id. (quoting Katz v. United States, 389 U.S. 347, 351 (1967)).

170. Id. (“[C]hecks are not confidential communications but negotiable instruments to be

used in commercial transactions.”). Understandably, this decision ruffled the feathers of the

liberals on the Court. The dissent pointed out that, although a bank’s customers might

voluntarily reveal their financial information to bank employees, they continue to reasonably

expect the information to be kept private. Id. at 449 (Brennan, J., dissenting) (“A bank

customer’s reasonable expectation is that, absent compulsion by legal process, the matters he

reveals to the bank will be utilized by the bank only for internal banking purposes.”).

171. 442 U.S. 735, 737 (1979).

172. Id.

173. Id. at 737-38.

1756 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

dialed.

174

The Court held that “[a]ll telephone users realize that

they must ‘convey’ phone numbers to the telephone company,”

making it unreasonable to expect such information to be kept pri-

vate.

175

The Court went on to invoke the freshly established Miller

doctrine, comparing information shared with a phone company to

financial records shared with a bank.

176

In doing so, the defendant

had “assumed the risk” that the company would reveal the informa-

tion to police.

177

The holdings of these two cases have fused into what can be

considered today as modern third-party doctrine. In short, any

objects or information voluntarily turned over to a third party, di-

rectly or indirectly, are not subject to any expectation of privacy that

society is willing to accept and are therefore not protected by the

Fourth Amendment.

178

This approach has drawn its fair share of

critics, almost all of whom contend that the doctrine does not ac-

curately reflect either people’s subjective expectation of privacy or

society’s willingness to accept it.

179

B. Carpenter and Third-Party Doctrine

For many scholars, the third-party doctrine has not aged well in

the era of big data. While a person’s decision to turn information

over to a third party may once have indicated that they lacked an

expectation of privacy, modern people routinely use the internet to

communicate and the cloud to store sensitive information.

180

In fact,

evidence suggests that average Americans consider many types of

digital information within the traditional Smith-Miller scope of

174. Id. at 741.

175. Id. at 742.

176. See id. at 744.

177. Id. Once again, this assertion was met by a fierce dissent objecting to the idea that a

person’s justifiable privacy interest is obliterated the moment they turn information over to

any third party, especially in situations in which they have no choice in the matter. Id. 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 other persons for other

purposes.”).

178. Kerr, supra note 158, at 563.

179. See Lucas Issacharoff & Kyle Wirshba, Restoring Reason to the Third Party Doctrine,

100 M

INN.L.REV. 985, 992-93 (2016).

180. Id. at 993.

2021] THE QUALITATIVE FOURTH AMENDMENT 1757

third-party exceptions more private than certain other areas that

are protected by the Fourth Amendment.

181

On some level, this reflects of a problem that existed long before

the advent of the cloud, a problem recognized by the dissenters in

the Smith and Miller cases.

182

Namely, there is a difference between

information turned over to a single source out of necessity and

information voluntarily disclosed to the public at large. Fourth

Amendment scholar Sherry Colb points out that “treating expo-

sure to a limited audience as identical to exposure to the world,

means failing to recognize degrees of privacy in the Fourth Amend-

ment context.”

183

These “degrees of privacy” have always existed;

they have simply become more apparent as advancing technology

has made it easier to access sensitive information.

184

It is not un-

reasonable to suggest that when people take what is private and

make it public, they have forfeited their expectation of privacy.

185

But what they “seek[ ] to preserve as private, even in an area

accessible to the public, may be constitutionally protected.”

186

The Court seemed to recognize this problem when it rendered its

decision in Carpenter.

187

It referenced the “seismic shifts in digital

technology” that have allowed detailed tracking of everyone with a

smartphone, as well as the fact that such location data is not really

voluntarily “shared” with the cell service companies.

188

Critically, it

also called back to a notion expressed in Riley v. California that an

individual can have a diminished privacy interest without com-

pletely abrogating all Fourth Amendment protection.

189

The Court

used this reasoning (and a good bit of legal finagling) to find third-

party doctrine inapplicable without overruling any part of either

181. See, e.g., CHRISTOPHER SLOBOGIN, PRIVACY AT RISK:THE NEW GOVERNMENT

SURVEILLANCE AND THE FOURTH AMENDMENT 184-86 (2007) (finding that most people consider

a search of private emails more intrusive than pat downs or vehicle searches).

182. See supra notes 170, 177.

183. Sherry F. Colb, What Is a Search? Two Conceptual Flaws in Fourth Amendment

Doctrine and Some Hints of a Remedy, 55 S

TAN.L.REV. 119, 122 (2002).

184. See id.

185. Id. at 124-26.

186. Katz v. United States, 389 U.S. 347, 351-52 (1967).

187. Carpenter v. United States, 138 S. Ct. 2206 (2018).

188. Id.

189. Id. at 2219; see also Riley v. California, 573 U.S. 373, 392 (2014) (“The fact that an

arrestee has diminished privacy interests does not mean that the Fourth Amendment falls

out of the picture entirely.”).

1758 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

Smith or Miller.

190

Of course, the only way to manage this was by

focusing on the content of the information, rather than its

location.

191

This would seem to suggest that some categories of

information, regardless of whether they have been “voluntarily”

disclosed to a third-party corporation, are simply too private to allow

an unsympathetic traditional application of third-party doctrine.

C. Third-Party Doctrine and the Obtainable Information

Standard

Many commentators believe that, whatever the third-party

doctrine was once worth, it has lost its usefulness and should be

retired in favor of a more modern understanding of privacy expecta-

tions. This may very well be true. However, it should be noted that

the obtainable information standard does not require the doctrine

to be overruled or even modified any more than it already has been

by Carpenter.

192

In other words, the standard would work even if the

Court chooses to retain third-party doctrine.

The third-party doctrine is based on the presumption that infor-

mation willingly turned over to a third party has been “expose[d] to

the public” and therefore necessarily fails the Katz test.

193

If need

be, this presumption could carry over to an information-based

approach. If information has fallen into the hands of a third party,

the government need not resort to trespass or surveillance to obtain

it. So long as the third party is willing to hand the information over,

the third-party doctrine can be upheld with the obtainable informa-

tion framework.

Taking the Court’s two landmark decisions in this area as

examples, it is easy to see how the obtainable information standard

might apply. In the case of Mitch Miller, his bank records were

voluntarily disclosed to the bank itself, at least in the sense that he

190. See Carpenter, 138 S. Ct. at 2220.

191. Id. at 2219 (“There is a world of difference between the limited types of personal

information addressed in Smith and Miller and the exhaustive chronicle of location

information casually collected by wireless carriers today.”).

192. See id. at 2217 (refusing to extend the Smith-Miller standard to cell phone location

records).

193. See United States v. Miller, 425 U.S. 435, 442 (1976) (quoting Katz v. United States,

389 U.S. 347, 351 (1967)).

2021] THE QUALITATIVE FOURTH AMENDMENT 1759

knew his bank had access to the information contained within

them.

194

Rather than resorting to physical intrusion or surveillance,

the government simply obtained the information by taking it from

the bank itself.

195

As such, there was no violation of the obtainable

information standard.

The Smith case is more troubling, as the installation of a pen

196

Furthermore, such a device almost certainly seems to fall within the

scope of “surveillance technology” as discussed earlier in this

Note.

197

However, the question is no less easily resolved. As the

Court pointed out in Smith, unlike the content of a phone conversa-

tion, the number being dialed is willingly turned over to the phone

company, as the phone call could not be carried out otherwise.

198

Therefore, although the government in this case did resort to

surveillance to gather information, that information was not

otherwise unavailable. The government could theoretically have

casually acquired the information indirectly through the phone

company, which had full access to the numbers being dialed by the

defendant.

199

As such, the information at stake in Smith can be

construed to comply with the obtainable information standard to the

extent that the use of surveillance technology was not necessary.

Furthermore, this point raises a compelling distinction between

the information at issue in Smith and in Carpenter. In Smith, the

phone company’s access to the numbers its clients dialed was not for

the purpose of creating a log of which numbers were dialed or for

identifying the people at either end of a conversation.

200

Rather, it

was a collateral necessity of the company’s need to connect its cus-

tomers with the intended recipients of their phone calls.

201

Using

this logic, it cannot be maintained that the technology allowing the

company’s access to the numbers Smith dialed was primarily used

for the purpose of gathering the type of information at issue in that

194. See id.

195. See id. at 437-38.

196. See Smith v. Maryland, 442 U.S. 735, 737 (1979).

197. See supra Part II.B.2.b.

198. Smith, 442 U.S. at 742.

199. See id.

200. See id.

201. Id.

1760 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

case. On the other hand, the CSLI data in Carpenter, whether ac-

cessed by the government or by the phone company, was gathered

and catalogued specifically for the purpose of tracking the phone’s

location.

202

Therefore, the primary purpose of the computer systems

that compile CSLI is, in fact, to gather the very type of information

at issue in that case.

203

In this sense, the obtainable information standard bridges the

gap between traditional third-party doctrine and the holding of

Carpenter, addressing the fears of many academic commentators on

the matter.

204

Under the standard, it would not matter whether the

government or a third party initially obtained the information at

issue. Only the nature of the information itself and the technology

used to obtain it would be relevant to the inquiry. In doing so, the

obtainable information standard preserves the third-party doctrine’s

legitimate public interests without risking betrayal of the increas-

ingly complex degrees of privacy afforded by modern technology.

205

CONCLUSION

The legacy of Justice Harlan’s two-prong test for identifying con-

stitutionally protected interests is prolific and yet decidedly mixed.

Traditional application of the Fourth Amendment had been rela-

tively simple: either the government physically intruded upon a

specific constitutionally protected area or there was no violation

whatsoever.

206

But Katz opened the door for government surveil-

lance to be judged under the framework of the Fourth Amendment,

even when such surveillance did not involve physical intrusion into

a protected space.

207

Such a major development prompted a slew of

new questions and concerns, few of which were adequately ad-

dressed by the ambiguity and circularity of the “reasonable

202. See Carpenter v. United States, 138 S. Ct. 2206, 2212 (2018); see also Lacambra, supra

note 73.

203. See Carpenter, 138 S. Ct. at 2212.

204. See, e.g., Melody J. Brannon, Carpenter v. United States: Building a Property-Based

Fourth Amendment Approach for Digital Data, 33 C

RIM.JUST. 20, 26 (2019) (stating that the

third-party doctrine is “on life support” after Carpenter).

205. See Colb, supra note 183, at 122.

206. See, e.g., Olmstead v. United States, 277 U.S. 438, 464 (1928) (stating that the Fourth

Amendment applies only to “material things”).

207. See Katz v. United States, 389 U.S. 347, 353 (1967).

2021] THE QUALITATIVE FOURTH AMENDMENT 1761

expectation of privacy.” It necessarily required the Court to broaden

its focus beyond the physical realm and allow the Fourth Amend-

ment to protect information as well as property.

The Supreme Court has avoided explicitly stating this reality for

over half a century, but a cursory review of the relevant case law

indicates that it has been trending in this direction. Carpenter was

just one more nail (albeit a decisive one) in the proverbial coffin of

the strictly textualist property-based approach to Fourth Amend-

ment doctrine. Scholars may find ways to force the round pegs of

Carpenter and Jones into the square holes of the property-based

approach or the historical approach,

208

but these are temporary

solutions which serve only to postpone the inevitable. As it turns

out, modern Fourth Amendment law is tied to both the quantity and

quality of the information obtained.

209

Having recognized this, it is simple to create an all-encompassing

information-based standard for cases of warrantless government

surveillance that both accounts for all the Court’s post-Katz holdings

and provides a clear roadmap for the future: absent probable cause,

the Fourth Amendment prevents the government from obtaining

information that could not otherwise be obtained without resorting

to surveillance technology or trespassing on private property.

210

Provided a proper definition for “surveillance technology” and a

rough idea of how this standard would have applied to other cases,

the obtainable information rule could provide some much-needed

clarity for lower courts.

It may be true that the Katz test is somewhat “circular” and “sub-

jective,”

211

but it has done a far better job accounting for society’s

evolving privacy values than a traditional application of Fourth

208. See, e.g., Burrus & Knight, supra note 20, at 111; Brannon, supra note 204, at 24-26.

209. See Carpenter v. United States, 138 S. Ct. 2206, 2223 (2018) (deciding based on the

“depth, breadth, and comprehensive reach” of CSLI).

210. See Colb, supra note 183, at 125.

211. See Kyllo v. United States, 533 U.S. 27, 34 (2001).

1762 WILLIAM & MARY LAW REVIEW [Vol. 62:1727

Amendment doctrine. Now that the digital age is well underway, it

deserves to be cemented in a clean and clear rule for checking gov-

ernment surveillance.

Joshua L. Wagner

* William & Mary Law School, J.D. candidate, 2021. I would like to thank Professors

Rebecca Green and Paul Marcus for their helpful comments and suggestions, as well as their

wonderful classes, which inspired this Note. I would also like to thank Jennifer Kleine for her

invaluable editorial assistance and the entire staff of the William & Mary Law Review who

worked tirelessly to make my work presentable.