Bailment Law as Part of a Property-Based Fourth Amendment Framework

Jeremy Hall
Volume 28
,  Issue 1


“We kill people based on metadata,” affirmed former National Security Agency (“NSA”) and Central Intelligence Agency (“CIA”) director, General Michael Hayden, at a debate at Johns Hopkins University in 2014.1David Cole, We Kill People Based on Metadata, N.Y. Rev. Books (May 10, 2014), (citing Gen. Michael Hayden, in Johns Hopkins University, The Johns Hopkins Foreign Affairs Symposium Presents: The Price of Privacy: Re-Evaluating the NSA, YouTube (April 7, 2014), The “people” General Hayden was talking about, of course, are terrorists—and various US government metadata collection programs have been a key part of the global war on terror since the 9/11 attacks.2See, e.g., Glenn Greenwald, NSA Collecting Phone Records of Millions of Verizon Customers Daily, Guardian (June 6, 2013, 6:05 AM), After the Snowden revelations regarding the NSA’s surveillance programs, including bulk metadata collection, President Obama claimed that “[w]e know of at least 50 threats that have been averted because of this information.”3Justin Elliot & Theordric Meyer, Claim on “Attacks Thwarted” by NSA Spreads Despite Lack of Evidence, ProPublica (Oct. 23, 2013, 8:59 AM), numerous claims by government officials regarding the number of terrorist plots foiled by the NSA programs).

What is metadata? Broadly speaking, metadata is simply “data about data.”4See Metadata,, In the electronic communication context, “metadata” is distinguished from “content”—while content “reflects the substance of an electronic communication,” metadata reflects “all other information about the communication, such as parties, time, and duration.”5Jonathan Mayer, Patrick Mutchler & John C. Mitchell, Evaluating the Privacy Properties of Telephone Metadata, 113 PNAS 5536, 5536 (2016); see also ACLU v. Clapper, 785 F.3d 787, 793 (2d Cir. 2015) (“Unlike what is gleaned from the more traditional investigative practice of wiretapping, telephone metadata do not include the voice content of telephone conversations. Rather, they include details about telephone calls, including, for example, the length of a call, the phone number from which the call was made, and the phone number called.”). The NSA’s bulk metadata collection programs have been the subject of intense scrutiny, controversy, and even litigation,6See, e.g., Clapper, 785 F.3d at 793 (“As in the 1970s, the revelation of this [bulk metadata collection] program has generated considerable public attention and concern about the intrusion of government into private matters.”). largely stemming from concerns that the programs violate a person’s Fourth Amendment right to be free from unreasonable searches and seizures.7U.S. Const. amend. IV. Debate over NSA programs has continued during temporary extensions of statutory authority.8See Sarah Ferris, John Bresnahan & Heather Caygle, Bipartisan Revolt Upends Vote to Reauthorize FISA, Politico (May 27, 2020, 11:04 PM),; Margaret Taylor, What Happened to FISA Reform?, Lawfare (Mar. 17, 2020, 3:06 PM),; George W. Croner, FISA Renewal Controversy: The Suddenly Very Conspicuous Foreign Intelligence Surveillance Act, Foreign Policy Research Institute(Nov. 7, 2019),

But the NSA is not the only actor in the metadata collecting business—domestic law enforcement agencies can also access and use metadata for investigative purposes, without a warrant, through the third-party doctrine.9See, e.g., Clapper, 785 F.3d at 793, 822. The third-party doctrine, which one commentator described as holding that “anything you tell anyone else . . . does not fall within the protections of the Fourth Amendment,”10Laura K. Donohue, Functional Equivalence and Residual Rights Post-Carpenter: Framing A Test Consistent with Precedent and Original Meaning, 2018 Sup. Ct. Rev. 347, 351 (2018). arose as an exception to the Supreme Court’s “reasonable expectation of privacy” test set out in Katz v. United States.11389 U.S. 347 (1967). As outlined in Justice Harlan’s concurrence in Katz, the reasonable expectation of privacy test has two requirements: “first that a person ha[s] exhibited an actual (subjective) expectation of privacy, and, second, that the expectation be one that society is prepared to recognize as ‘reasonable.’”12Id. at 361 (Harlan, J., concurring). Subsequently, in United States v. Miller13425 U.S. 435 (1976). and Smith v. Maryland,14442 U.S. 735 (1979). the Supreme Court established the third-party doctrine, which “asserts that a person cannot have a protected privacy interest in information voluntarily turned over to a third party.”15See Alexandra Carthew, Comment, Searches and Seizures – Fourth Amendment and Reasonableness in General: Protection of Privacy Interests in the Digital Age, 94 N.D. L. Rev. 197, 206 (2019) (citing Smith, 442 U.S. at 744; Miller, 425 U.S. at 440–43); see also Peter C. Ormerod & Lawrence J. Trautman, A Descriptive Analysis of the Fourth Amendment and the Third-Party Doctrine in the Digital Age, 28 Alb. L.J. Sci. & Tech. 73, 110 (2018) (“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.’” (citing Daniel J. Solove, A Taxonomy of Privacy, 154 U. PA. L. Rev. 477, 526 (2006)).

The third-party doctrine, which has been widely criticized by a broad range of scholars,16See, e.g., Donohue, supranote 10, at 351 (listing “[i]ntellectually diverse scholars” who have criticized the doctrine). was recently addressed in 2018 by the Supreme Court in Carpenter v. United States.17138 S. Ct. 2206 (2018). At issue in that case was warrantless law enforcement collection of a type of telephone metadata called cell-site location information (“CSLI”).18Id. at 2211–12. Ultimately, the Court held that warrantless access to seven or more days’ worth of CSLI violated an individual’s “legitimate expectation of privacy.”19Id. at 2216, 2217 n.3 (“It is sufficient for our purposes today to hold that accessing seven days of CSLI constitutes a Fourth Amendment search.”). The majority maintained that the third-party doctrine of Smith and Miller was still intact, emphasizing that the decision in Carpenter was a “narrow one,” and did not address “matters not before us.”20Id. at 2220.

The narrowness of the Court’s holding in Carpenter, combined with “conceptual shortcomings” in the majority’s reasoning and dissents by Justices Thomas and Gorsuch in particular, have led some commentators to predict that “the case will eventually be bigger than its holding.”21See Trevor Burrus & James Knight, Katz Nipped and Katz Cradled: Carpenter and the Evolving Fourth Amendment, 2017–2018 Cato Sup. Ct. Rev. 79, 80 (“Carpenter will likely be seen by future generations as the beginning of significant changes to the law of the Fourth Amendment.”). Justice Gorsuch’s dissent specifically has been described as an “opening salvo” in a “career-long attempt to re-work the Court’s Fourth Amendment jurisprudence.”22Id. Justice Gorsuch stated that “many types of information now covered by the third-party doctrine should be protected by the Fourth Amendment.”23Id. He argued that instead of following the Katz “reasonable expectation of privacy” test, the Court could return to the traditional pre-Katz approach, which asked simply “if a house, paper, or effect was yours under law.”24Carpenter, 138 S. Ct. at 2267–68 (Gorsuch, J., dissenting) (italics in original).

While Justice Gorsuch left many questions unanswered, he suggested a framework for further research and outlined five starting principles.25See id. at 2268–71 (Gorsuch, J., dissenting) (outlining five principles for updating the traditional, property-focused approach); see also discussion infra section I.C.3; Nicholas A. Kahn-Fogel, Property, Privacy, and Justice Gorsuch’s Expansive Fourth Amendment Originalism, 43 Harv. J. L. & Pub. Pol’y 425, 429 (“Although Justice Gorsuch offered preliminary thoughts on this rubric, his opinion left open important questions, including the sources of law to which the Court should look in identifying property interests; the breadth of the definitions of ‘papers’ and ‘effects’ and the kinds of property closely enough associated with the person for potential implication of Fourth Amendment rights; and the ways in which government conduct impinging on such property interests might trigger Fourth Amendment protection.”). This Comment focuses on Justice Gorsuch’s first principle: “the fact that a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them.”26Carpenter, 138 S. Ct. at 2268. In his brief discussion of this point, Justice Gorsuch raised the possibility that the “ancient principles” of bailment law “may help us address modern data cases too,” stating that “[j]ust because you entrust your data—in some cases, your modern-day papers and effects—to a third party may not mean you lose any Fourth Amendment interest in its contents.”27Id. at 2269.

In essence, a bailment is a “delivery of personal property by one person (the bailor) to another (the bailee) who holds the property for a certain purpose.”28Bailment, Black’s Law Dictionary (11th ed. 2019). The relationship between bailor and bailee imposes certain rights and obligations on both parties with respect to the property in question.29See, e.g., 8 C.J.S. Bailments § 55 (2019) (“Once a bailment relationship has been established, the law imposes upon the bailee certain duties and obligations with respect to the bailed property in her possession.”); id. § 36. This Comment maintains that bailment law—specifically, the principle that a bailee is held strictly liable for conversion for misdelivery of a bailment—provides a helpful foundation for an updated traditional, property-focused Fourth Amendment framework.30This Comment focuses on the bailment law portion of Justice Gorsuch’s proposal for an updated traditional Fourth Amendment framework. For an examination of the positive law aspect of Gorsuch’s proposed Fourth Amendment framework, see William Baude & James Y. Stern, The Positive Law Model of the Fourth Amendment, 129 Harv. L. Rev. 1821, 1823 (2016). Professors Baude and Stern argue that “[i]nstead of making Fourth Amendment protection hinge on whether it is ‘reasonable’ to expect privacy in a given situation, a court should ask whether government officials have engaged in an investigative act that would be unlawful for a similarly situated private actor to perform.” Id. at 1825. Baude and Stern note that aspects of positive law that should apply in the Fourth Amendment context include “property law, privacy torts, consumer laws, eavesdropping and wiretapping legislation, anti-stalking statutes, and other provisions of law generally applicable to private actors.” Id. at 1823. For a critique of Baude and Stern, see Richard M. Re, The Positive Law Floor, 129 Harv. L. Rev. F. 313 (2016). Professor Richard Re argues that “[i]n giving the positive law model its most thorough elaboration and defense, Baude and Stern push its logic too far.” Id. at 314. In contrast to what Re calls the “positive law ceiling” approach of Baude and Stern, Re calls his approach the “positive law floor”—emphasizing that the better approach is “learning from analogies to private parties without being limited by them.” Id. Professor Laura Donohue also addressed the role and limits of positive law in the Fourth Amendment context in a recent article. See Donohue, supra note 10, at 400–01 (“Where federal statutory law or regulatory measures have privileged certain actors’ control over information and denied access to the information to others, government intrusions may constitute a search or seizure within the meaning of the Fourth Amendment.” (italics in original)). Professor Donohue agrees with Professor Re on the floor versus ceiling distinction, rather than Professors Baude and Stern. See id. at 405 n.287.

To that end, Part I of this Comment explores the background of Fourth Amendment jurisprudence, surveying its doctrinal evolution in the Supreme Court. Part II explores how bailment law provides a crucial piece of an updated property-based framework for Fourth Amendment jurisprudence. Additionally, considering Justice Gorsuch’s admonition that Mr. Carpenter “did not invoke the law of property or any analogies to the common law,”31Carpenter, 138 S. Ct. at 2272 (Gorsuch, J., dissenting). Part II then identifies how litigants could make arguments based on bailment law in cases similar to Carpenter.

I.     The Evolution of the Supreme Court’s Fourth Amendment Jurisprudence

The Fourth Amendment states that “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated” and requires that warrants have “probable cause, supported by Oath or affirmation, and particularly describ[e] the place to be searched, and the persons or things to be seized.”32U.S. Const. amend. IV. The Fourth Amendment was designed to “secure liberty,”33See Donohue, supra note 10, at 347 (citing 1 Annals of Cong. 443, 446, 449 (1789) (Joseph Gales ed., 1834)). and it “reinforced the right of the people, as sovereign, to determine the conditions under which the government could intrude in their lives.”34Id. at 347–48 (citing Camara v. Mun. Ct. of S.F., 387 U.S. 523, 528 (1967); Boyd v. United States, 116 U.S. 616, 630 (1886)). The Fourth Amendment was adopted in “response to the reviled ‘general warrants’ and ‘writs of assistance’ of the colonial era, which allowed British officers to rummage through homes in an unrestrained search for evidence of criminal activity.”35Carpenter, 138 S. Ct. at 2213 (quoting Riley v. California, 573 U.S. 373, 403 (2014)).

In contrast to the view that the Fourth Amendment originally merely required that searches and seizures be “reasonable,”36See Laura K. Donohue, The Original Fourth Amendment, 83 U. Chi. L. Rev. 1181, 1185 n.13 (2016) (citing Akhil Reed Amar, The Fourth Amendment, Boston, and the Writs of Assistance, 30 Suffolk U. L. Rev. 53, 55 (1996)). Professor Laura Donohue argues that the Fourth Amendment should be understood as “a prohibition on general search and seizure authorities and a requirement for specific warrants.”37Id. at 1193. Donohue states that “the first clause outlaws promiscuous search and seizure” and the second clause “clarifies precisely what will be required for a particularized warrant to be valid.”38Id. (“The government could not violate the right against search and seizure of one’s person, house, papers, or effects absent either a felony arrest or a warrant meeting the requirements detailed in the second clause.”). At the time the Fourth Amendment was drafted, “unreasonable” simply meant “against the reason of the common law,” rather than the modern “relativistic” sense of evaluating “what could be considered more or less reasonable.”39Id. at 1192–93.

In early cases, the Supreme Court utilized traditional property law concepts to determine if the government had violated the Fourth Amendment.40See, e.g., United States v. Jones, 565 U.S. 400, 405 (2012) (“The text of the Fourth Amendment reflects its close connection to property . . . [c]onsistent with this understanding, our Fourth Amendment jurisprudence was tied to common-law trespass, at least until the latter half of the 20th century.” (citing Kyllo v. United States, 533 U.S. 27, 31 (2001))); see also Orin S. Kerr, The Fourth Amendment and New Technologies: Constitutional Myths and the Case for Caution, 102 Mich. L. Rev. 801, 816 (2004); infra note 46. Then, in Katz v. United States, the Court transformed Fourth Amendment jurisprudence by adopting a “reasonable expectation of privacy” test.41Katz v. United States, 389 U.S. 347, 360–61 (1967) (Harlan, J., concurring). In United States v. Miller and Smith v. Maryland, the Court carved out an exception to the Katz rule which has become known as the third-party doctrine.42Smith v. Maryland, 442 U.S. 735, 743–44 (1979); United States v. Miller, 425 U.S. 435, 443 (1976). Recently, in United States v. Jones,43565 U.S. 400 (2012). the Court stated that Katz had not extinguished the traditional test—rather, the two tests exist as alternative ways of identifying when an individual’s Fourth Amendment rights have been violated.44Id. at 406–07. Finally, in Carpenter v. United States, the Court—rather than formally overturning Miller and Smith or even Katz itself—instead created an exception to the third-party doctrine for warrantless CSLI collection lasting seven or more days.45138 S. Ct. 2206, 2217 n.3 (2018).

A.     The Early Cases: Property Law Framework

The Supreme Court’s early interpretations of the Fourth Amendment utilized a “property-centric” approach, closely adhering to the text of the amendment.46See, e.g., Burrus & Knight, supra note 21, at 82; see also Jones, 565 U.S. at 405 (citing Kyllo v. United States, 533 U.S. 27, 31 (2001)); Daniel de Zayas, Carpenter v. United States and the Emerging Expectation of Privacy in Data Comprehensiveness Applied to Browsing History, 68 Am. U. L. Rev. 2209, 2223 (2019) (“The Court’s early Fourth Amendment jurisprudence interpreted the Fourth Amendment through a property-rights framework.”); Mihailis E. Diamantis, Privileging Privacy: Confidentiality as a Source of Fourth Amendment Protection, 21 U. Pa. J. Const. L. 485, 487 (2018) (“In the nineteenth century, Fourth Amendment doctrine centered on preventing unwarranted physical intrusions by the government.”); Donohue, supra note 10, at 348 (“For decades, the Court adopted a property-based approach, tying the doctrine to common-law trespass, which prioritized the question of whether a physical intrusion had occurred ‘on a constitutionally protected area.’”); Nita A. Farahany, Searching Secrets, 160 U. Pa. L. Rev. 1239, 1245 (2012) (“[P]roperty law has held a stranglehold on Fourth Amendment doctrine.”); H. Brian Holland, A Cognitive Theory of the Third-Party Doctrine and Digital Papers, 91 Temp. L. Rev. 55, 65 (2018) (“Prior to 1967, a Fourth Amendment search was defined as a ‘physical intrusion [into] a constitutionally protected area in order to obtain information.’” (citing United States v. Knotts, 460 U.S. 276, 286 (1983))); Kerr, supra note 40 at 816. In a series of cases examined below, the Court used that approach to deal with various physical intrusions affecting individuals’ physical property, such as “houses, papers, and effects.”47See Carthew, supra note 15, at 200 (“The Fourth Amendment has been judicially interpreted as protecting the privacy and security of individuals against arbitrary invasions by government officials.” (citing Camara v. Mun. Ct. of S.F., 387 U.S. 523, 528 (1967))). Under this approach, the Court’s Fourth Amendment jurisprudence largely focused on “whether a search had taken place,” defining a search as a “physical intrusion [into] a constitutionally protected area in order to obtain information.”48See Holland, supra note 46, at 65 (citing Knotts, 460 U.S. at 286 (Brennan, J., concurring)). Holland notes that pre-Katz, the Court defined “protected area” as “an individual’s property ownership or possessory rights in the object or location of the search,” and “physical intrusion” by “reference to common law trespass.” Id. (citing Jones, 565 U.S. at 405).

1.     Examples of the Court Applying a Property Law Framework in Early Cases

For example, in Ex parte Jackson,4996 U.S. 727 (1877). the Court applied the Fourth Amendment to different kinds of mail, holding that—unlike newspapers, magazines, and pamphlets, which are “purposely” left “open to inspection”50Id. at 733.—letters and sealed packages were protected under the Fourth Amendment “as if they were retained by the parties forwarding them in their own domiciles.”51Id. The Court identified that the rights of individuals “to be secure in their papers against unreasonable searches and seizures extends to their papers, thus closed against inspection, wherever they may be,” and held that sealed mail could only be accessed by the government through the same kind of particular warrant required for searching papers in someone’s house.52See id.; see also Samuel D. Thomas, Collect Call for Clarification: How Carpenter Has (and Has Not) Changed Modern Fourth Amendment Jurisprudence, 60 B.C. L. Rev. 2221, 2228–29 (2019) (drawing attention to how the Court’s decision in Ex parte Jackson echoed language from the influential British case Entick v. Carrington, 19 Howell’s St. Tr. 1029, 1066–67 (C.P. 1765)).

The Court subsequently recognized, in Weeks v. United States,53232 U.S. 383 (1914). that the Fourth Amendment’s protection against warrantless searches of one’s home, papers, and effects extends even to a person accused of a crime.54Id. at 392–93. In Weeks, the Court reversed the conviction of an individual after the lower court admitted into evidence letters taken from the house of the individual by a United States marshal without a warrant.55Id. at 393, 398. The Court noted that “[i]f letters and private documents can thus be seized and held and used in evidence against a citizen accused of an offense,” the Fourth Amendment “is of no value, and, so far as those thus placed are concerned, might as well be stricken from the Constitution.”56Id. at 393. The Court observed that the Fourth Amendment was adopted on the principle that “a man’s house was his castle and not to be invaded by any general authority to search and seize his goods and papers.”57Id. at 390.

In Agnello v. United States,58269 U.S. 20 (1925). the Court similarly held that, while the government has a right to conduct a contemporaneous warrantless search of a person “lawfully arrested while committing crime,” and even to search the location of the arrest, that right “does not extend to other places.”59Id. at 30–32. In Agnello, police arrested an individual involved in a suspected drug deal and proceeded to search his house, which was several blocks away from the location of the arrest.60Id. at 29–30. The Court observed that “it has always been assumed that one’s house cannot lawfully be searched without a search warrant, except as an incident to a lawful arrest therein.”61Id. at 32. As the search of the individual’s home was not “incident to a lawful arrest,” it violated the Fourth Amendment—which the Court held extends equally to “those justly suspected or accused, as well as to the innocent.”62Id. The Court noted that “[t]he search of a private dwelling without a warrant is in itself unreasonable and abhorrent to our laws” and that Congress had enacted special restrictions for the conditions under which a warrant for the search of a private dwelling could be issued. See id. at 32–33.

These cases illustrate the property framework underlying the Court’s early Fourth Amendment jurisprudence and show how concerned the Court was with protecting private “houses, papers, and effects” against warrantless intrusion by the government.63See Carpenter v. United States, 138 S. Ct. 2206, 2239–40 (Thomas, J., dissenting) (“[T]he Fourth Amendment references ‘[t]he right of the people to be secure.’ It then qualifies that right by limiting it to ‘persons’ and three specific types of property: ‘houses, papers, and effects.’ By connecting the right to be secure to these four specific objects, ‘[t]he text of the Fourth Amendment reflects its close connection to property.’” (quoting United States v. Jones, 565 U.S. 400, 405 (2012))).

2.     Persistence of the Property Law Framework Despite Technological Change

Changes in technology did not initially lead to a change in Fourth Amendment doctrine.64See Carthew, supra note 15, at 201. In Olmstead v. United States,65277 U.S. 438 (1928). which has been called the “classic case” illustrating the Court’s property approach to the Fourth Amendment,66See Kerr, supra note 40, at 816 (noting that Olmstead “was the first wiretapping case decided by the Supreme Court”); see also Kahn-Fogel, supra note 25, at 427 (“The Court’s opinion in Olmstead v. United States was the quintessential expression of this [trespass] model.”). the Court extended the physical trespass approach to the wiretapping context, distinguishing letters, which are protected under the Fourth Amendment, from telegraph or telephone messages, which are not.67Olmstead, 277 U.S. 438, 464 (1928). In Olmstead, federal prohibition officers intercepted telephone messages without trespassing on the defendants’ property by placing wiretaps on the street near the defendants’ houses and in the basement of an office building.68Id. at 456–57. Rejecting an argument by analogy to Ex parte Jackson, the Court drew a difference between sealed letters and telephone messages, reasoning that “[t]he evidence was secured by the use of the sense of hearing and that only,” and “[t]here was no entry of the houses or offices of the defendants.”69Id. at 464. The Court went on to note that “[h]ere those who intercepted the projected voices were not in the house of either party to the conversation.” Id. at 466.

Justice Brandeis dissented in Olmstead, arguing that “clauses guaranteeing to the individual protection against specific abuses of power, must have a similar capacity of adaptation to a changing world.”70Id. at 472 (Brandeis, J., dissenting). Brandeis, joined explicitly by Justice Stone and implicitly by Justice Butler, offered a different approach than the property-focused majority.71See Kerr, supra note 40, at 817 n.84. Brandeis focused on the privacy of the defendants, rather than the physical location of the telephone wires, stating that “every unjustifiable intrusion by the Government upon the privacy of the individual, whatever the means employed, must be deemed a violation of the Fourth Amendment.”72Olmstead, 277 U.S. at 478–79 (Brandeis, J., dissenting).

Justice Brandeis’s dissent would lead to forty years of scholarly commentary against the “narrow trespass theory reasoning of Olmstead,” and ultimately foreshadowed the Court’s decision in Katz.73See Paul Ohm, The Many Revolutions of Carpenter, 32 Harv. J.L. & Tech. 357, 416 (2019). However, in 1928, all of that was the unknown future. The state of the Court’s Fourth Amendment jurisprudence at the time is summed up by the following passage from the Olmstead opinion:

Neither the cases we have cited nor any of the many federal decisions brought to our attention hold the Fourth Amendment to have been violated as against a defendant unless there has been an official search and seizure of his person, or such a seizure of his papers or his tangible material effects, or an actual physical invasion of his house ‘or curtilage’ for the purpose of making a seizure.74Olmstead, 277 U.S. at 466 (1928).

Professor Donohue observes that the Court’s failure in Olmstead was not in applying its property framework correctly—the telephone wires did “lay outside the home,” after all—but in “failing to recognize that through wiretapping, the government gained access to the intimate details of the speakers’ lives—details ensconced in their persons, houses, papers, and effects.”75See Donohue, supra note 10, at 348. The reaction of the other branches of government seems to support this view: Congress responded to Olmstead by making unauthorized wiretapping a federal crime, and President Roosevelt pardoned Mr. Olmstead, “restoring all of his constitutional rights, and remitting the $8,000 fine assessed against him, in addition to $2,288 in court costs.”76See Peter Winn, Katz and the Origins of the “Reasonable Expectation of Privacy” Test, 40 McGeorge L. Rev. 1, 2 n.6 (2009) (citation omitted). However, the effectiveness of the wiretapping section of the 1934 Federal Communications Act was “undercut dramatically” when the Justice Department interpreted it merely to prevent admission of wiretapping evidence in court but still allowed the wiretapping itself to legally take place. Kerr, supra note 40, at 845–46.

Despite the negative reaction to Olmstead, the Court continued to utilize the strict physical trespass rule. The Court concluded in Goldman v. United States77316 U.S. 129 (1942). and Silverman v. United States,78365 U.S. 505 (1961). respectively, that “microphones placed against the wall of an adjoining room did not trigger Fourth Amendment protections, but a ‘spike mike’ that physically pierced the property [via sound conveyed through a heating duct] did.”79Burrus & Knight, supra note 21, at 83 (citing Goldman, 316 U.S. at 135; Silverman, 365 U.S. at 511).

B.     Katz Changes Things

In 1967, the Supreme Court shifted from the property-focused approach to a privacy-focused approach in the key case of Katz v. United States. In Katz, FBI agents used a device attached to the outside of a public phone booth to listen to and record the defendant’s calls.80Katz v. United States, 389 U.S. 347, 348 (1967). The Court of Appeals, applying the test from Olmstead, held that the Fourth Amendment had not been violated because “[t]here was no physical entrance into the area occupied by [the petitioner].”81Id. at 348–49 (citing Katz v. United States, 369 F.2d 130, 134 (9th Cir. 1966)). Overturning what it called the “narrow,” “discredited” trespass test the Court had previously articulated in Olmstead, the Katz majority in the Supreme Court held that “the reach of th[e] [Fourth] Amendment cannot turn upon the presence or absence of a physical intrusion into any given enclosure.”82Id. at 353.

1.     Katz’s “Reasonable Expectation of Privacy” Test

In overturning Olmstead, the Katz Court went further than merely updating the Fourth Amendment in its application to new circumstances involving telephone technology.83See Burrus & Knight, supra note 21, at 83. Indeed, the Court fundamentally altered the scope of Fourth Amendment protections by asserting that “the Fourth Amendment protects people, not places.”84See Katz, 389 U.S. at 351. Professor Orin Kerr argues that the “popular view” of Katz—that the Supreme Court “rejected the property-based approach of Olmstead . . . and replaced it with a ‘reasonable expectation of privacy test’”—is misleading. See Kerr, supra note 40, at 817–18. Rather than adopting the privacy-focused dissent by Justice Brandeis in Olmstead—which Kerr points out was not mentioned anywhere in Katz—Kerr argues the Court in Katz merely returned to a “looser version” of the property-focused approach that it had previously been “tacitly applying” in prior cases such as Jones v. United States. See id. at 818–820 (citing Jones v. United States, 362 U.S. 257, 266 (1960) (holding that “subtle distinctions” of property law should not control a Fourth Amendment inquiry)). However, Kerr acknowledges that “[s]ubsequent dissents by Justice Harlan suggest that he may have had a broader, more amorphous concept in mind.” Id. at 823. Ultimately Kerr believes that Katz was a revolution “more on paper than in practice.” See id. at 824–27 (discussing cases after Katz where the Supreme Court affirmed pre-Katz precedents, and claiming that the Court has been “fairly consistent”). This idea resulted in an expansion of “the conception of the Fourth Amendment beyond guarding only against physical intrusions.”85See Carthew, supra note 15, at 201. While the majority did not articulate exactly how this new principle would work, Justice Harlan’s concurrence established the now-familiar two-prong “reasonable expectation of privacy” test.86See, e.g., Aaron L. Dalton, Carpenter v. United States: A New Era for Protecting Data Generated on Personal Technology, or A Mere Caveat?, 20 N.C.J.L. & Tech. On. 1, 11 (2018) (“Justice Harlan’s concurrence in Katz v. United States established the ‘reasonable expectations of privacy’ test for determining if law enforcement conducted a search that required a warrant under the Fourth Amendment.”); Andrew MacKie-Mason, The Private Search Doctrine After Jones, 126 Yale L.J. F. 326, 328 (2017) (“Justice Harlan’s concurrence, . . . has become the canonical statement of the test . . . .”); see also Terry v. Ohio, 392 U.S. 1, 9 (1968) (adopting the “reasonable expectation of privacy” test from Justice Harlan’s Katz concurrence). The first prong requires that a person must have “exhibited an actual (subjective) expectation of privacy.”87Katz, 389 U.S. at 361. The second prong requires that the expectation must “be one that society is prepared to recognize as ‘reasonable.’”88Id.

2.     The Third-Party Doctrine’s Limitation on Privacy

Regardless of how revolutionary one thinks Katz’s “reasonable expectation of privacy” formulation was,89See supranote 84. the Court subsequently created “broad exceptions” to the test, such as the third-party doctrine.90SeeDonohue, supra note 10, at 350. As articulated by the Supreme Court, the third-party doctrine “draw[s] a line between what a person keeps to himself and what he shares with others.”91See Carpenter v. United States, 138 S. Ct. 2206, 2216 (2018) (discussing the origins of the third-party doctrine); see also Baude & Stern, supra note 30, at 1871 (stating that the third-party doctrine essentially means that “under Katz [] people don’t have any Fourth Amendment protection for information given to a third party.”). Justice White predicted the rise of the third-party doctrine in his Katzconcurrence, recognizing the possibility of an “implie[d] assumption of risk” when someone shares information with another party.92See Donohue, supra note 10, at 350 (“When one man speaks to another he takes all the risks ordinarily inherent in so doing, including the risk that the man to whom he speaks will make public what he has heard. The Fourth Amendment does not protect against unreliable . . . associates.” (quoting Katz, 389 U.S. at 363 n** (White, J., concurring))).

In United States v. Miller, the Court officially articulated the third-party doctrine, relying on the assumption of risk theory to hold that the government could acquire bank records without a warrant, even if customers believed the records were confidential.93See United States v. Miller 425 U.S. 435, 443 (1976) (“This Court has held repeatedly that the Fourth Amendment does not prohibit the obtaining of information revealed to a third party and conveyed by him to Government authorities, even if the information is revealed on the assumption that it will be used only for a limited purpose and the confidence placed in the third party will not be betrayed.”); see also id. at 449 (Brennan, J., dissenting) (“Representatives of several banks testified at the suppression hearing that information in their possession regarding a customer’s account is deemed by them to be confidential.”); Thomas, supra note 52, at 2233 (“It made no difference in the analysis that the customers believed that the information was confidential and only used for a limited purpose.”). Essential to the Court’s holding was the conclusion that the records in question were the property of the bank, not the defendant.94SeeMiller, 425 U.S. at 440. The Court extended its conclusion that the records belonged to the bank to cover even the original checks and deposit slips signed by the defendant because they were “negotiable instruments to be used in commercial transactions.” See id. at 442. Miller is still cited by the Court as the origin of the third-party doctrine.95See, e.g., Carpenter, 138 S. Ct. at 2216 (“This third-party doctrine largely traces its roots to Miller.”).

Just three years later, in Smith v. Maryland, the Court extended the third-party doctrine to cover information shared with telephone companies.96See Smith v. Maryland, 442 U.S. 735, 745–46 (1979); see also Carpenter, 138 S. Ct. at 2216; Steven I. Friedland, Of Clouds and Clocks: Police Location Tracking in the Digital Age, 48 Tex. Tech L. Rev. 165, 176 (2015) (“Smith v. Maryland provided the other major bookend for the third-party rule of ‘knowing disclosure.’”). In Smith, the Court again applied the assumption of risk theory, this time to reason that the defendant “voluntarily conveyed” information to the phone company when he made a local phone call and thus “assumed the risk” that the phone company would reveal that information to the police.97See Smith, 442 U.S. at 744. In Smith, the information the government collected consisted of telephone numbers that the defendant had dialed—obtained through a pen register98See id. at 736 n.1 (“A pen register is a mechanical device that records the numbers dialed on a telephone by monitoring the electrical impulses caused when the dial on the telephone is released. It does not overhear oral communications and does not indicate whether calls are actually completed.” (quoting United States v. New York Tel. Co., 434 U.S. 159, 161 n. 1 (1977)).—but not the contents of the calls themselves.99See id. at 741.

The majority concluded that because the defendant voluntarily conveyed information to a third party, the defendant had no “legitimate” expectation of privacy.100See id. at 745. The majority’s reasoning did not go unchallenged—Justice Marshall argued in dissent that an essential element of assumption of risk is “some notion of choice” not present in that case,101See id. at 749–50 (Marshal, J., dissenting) (“It is idle to speak of ‘assuming’ risks in contexts where, as a practical matter, individuals have no realistic alternative.”). an argument later used by the majority in Carpenter to differentiate that case from Smith.102See Carpenter, 138 S. Ct. at 2220.

Scholars have widely criticized the third-party doctrine.103See, e.g., Orin S. Kerr, The Case for the Third-Party Doctrine, 107 Mich. L. Rev. 561, 563–64 (2009) (offering a defense of the third-party doctrine, while recognizing that “[t]he third-party doctrine is the Fourth Amendment rule scholars love to hate. It is the Lochner of search and seizure law, widely criticized as profoundly misguided”); see also Donohue, supra note 10, at 351 (identifying Professor Wayne LaFave, Professor Daniel Solove, and Professor Randy Barnett as critics of the third-party doctrine). Furthermore, as Professor Orin Kerr points out, “[o]ver a dozen state Supreme Courts have rejected the doctrine under parallel provisions of their state constitutions,” and even United States Supreme Court opinions applying the doctrine “ha[ve] never offered a clear argument in its favor.”104See Kerr, supra note 103, at 564–65 (arguing that the third-party doctrine, though widely criticized, serves two roles: first, to “maintain the technological neutrality of Fourth Amendment rules,” and second, “to provide ex ante clarity”). And while the majority in Carpenter carved out an exception to the third-party doctrine rather than overturn it,105See Carpenter, 138 S. Ct. at 2220 (declining to “extend Smith and Miller to the collection of CSLI”). Justice Gorsuch’s dissent was highly critical of the doctrine.106See id. at 2261–62 (Gorsuch, J., dissenting); see also discussion infra Section I.C.3.

3.     Despite Katz, the Property Framework is Still Viable

Recent cases show that the Court’s older property-based framework persists despite the introduction of the “reasonable expectation of privacy” in Katz—either because “Katz and its progeny did not completely excise property law from the Fourth Amendment,”107Burrus & Knight, supra note 21, at 93; see also Kerr, supra note 40, at 825 (“The Supreme Court’s opinions have sent conflicting rhetorical signals regarding the nature of the post-Katz Fourth Amendment.”). or because the Court subsequently re-introduced the property framework after Katz.108See, e.g., MacKie-Mason, supra note 86, at 328 (“In Jones, the Supreme Court once again changed direction and revived the ‘common-law trespassory test’ as an alternative to Katz’s reasonable expectation of privacy definition of search.”); Thomas, supra note 52, at 2236 (“[T]he Supreme Court began a slight return to using property law in its Fourth Amendment analysis.”); Alan Zorofchian, Comment, United States v. Ackerman: Revelation of Justice Gorsuch’s Fourth Amendment Decision-Making?, 2 Geo. L. Tech. Rev. 85, 87 (2017) (describing Jones as reintroducing the trespass test).

Regardless of which view of Supreme Court history is correct, in United States v. Jones, Justice Scalia’s majority opinion affirmed that “the Katz reasonable-expectation-of-privacy test has been added to, not substituted for, the common-law trespassory test.”109United States v. Jones 565 U.S. 400, 409 n.74 (2012); see also id. at 414 (Sotomayor, J., concurring) (“In Katz, this Court enlarged its then-prevailing focus on property rights by announcing that the reach of the Fourth Amendment does not ‘turn upon the presence or absence of a physical intrusion.’”). In Jones, the Court held that the installation of a tracking device on the defendant’s car was a Fourth Amendment search because “[t]he Government physically occupied private property for the purpose of obtaining information,” and the Court had “no doubt that such a physical intrusion would have been considered a ‘search’ within the meaning of the Fourth Amendment when it was adopted.”110See id. at 404–05.

In Jones, Justice Scalia summed up the Court’s Fourth Amendment jurisprudence by stating that “[a] trespass on ‘houses’ or ‘effects,’ or a Katz invasion of privacy, is not alone a search unless it is done to obtain information; and the obtaining of information is not alone a search unless it is achieved by such a trespass or invasion of privacy.”111See id. at 408 n.5. Thus Jones, as the “most significant case dealing with mass data surveillance before Carpenter,”112See Burrus & Knight, supra note 21, at 84. established that “[i]n a case where the government intrudes upon a constitutionally enumerated area—an ‘effect’ in the case of Jones—the Court has no need to turn to Katz.”113Kendall Van Ameyde, Defining the Limits of the Private-Search Doctrine in an Expanding Digital Landscape, 10 Alb. Gov’t L. Rev. 452, 462 (2017) (citing Courtney E. Walsh, Surveillance Technology and the Loss of Something a Lot Like Privacy: An Examination of the “Mosaic Theory” and the Limits of the Fourth Amendment, 24 St. Thomas L. Rev. 169, 224–25 (2012)).

C.     Carpenter v. United States Adds an Exception to the Third-Party Doctrine

In Carpenter, the first significant Fourth Amendment case since Justice Scalia’s death,114See Brandon R. Teachout, On Originalism’s Originality: The Supreme Court’s Historical Analysis of the Fourth Amendment from Boyd to Carpenter, 55 Tulsa L. Rev. 63, 105 (2019). the Court dealt with the question of “whether the Government conducts a search under the Fourth Amendment when it accesses historical cell phone records that provide a comprehensive chronicle of the user’s past movements.”115Carpenter v. United States, 138 S. Ct. 2206, 2211 (2018). For discussion of the facts of the case and lower court decisions leading to the Supreme Court’s decision in Carpenter, see Stephen E. Henderson, Carpenter v. United States and the Fourth Amendment: The Best Way Forward, 26 Wm. & Mary Bill Rts. J. 495 (2017); Ormerod & Trautman, supra note 15, at 127. Chief Justice Roberts’s majority opinion concluded that the answer was yes.116See Carpenter, 138 S. Ct. at 2223. Carpenter had four dissenting opinions, offering “three separate tacks.”117See Teachout, supra note 114, at 106 (characterizing the four dissenting opinions). Reactions to Carpenter have been mixed. See de Zayas, supra note 46, at 2243 (describing the opinions of various scholars responding to Carpenter).

1.     Facts and Procedural History of Carpenter

In 2011, police attempting to catch a group responsible for robbing stores in Detroit acquired a list of cell phone numbers associated with the group from a suspect in the case, who identified fifteen other accomplices.118Carpenter, 138 S. Ct. at 2212. Prosecutors then used that information to “obtain cell phone records for petitioner Timothy Carpenter and several other suspects” through “court orders under the Stored Communications Act.”119Id. The requests were granted, and judges ordered MetroPCS and Sprint—Carpenter’s wireless carriers—to disclose CSLI for Carpenter’s cell phone “‘at call origination and at call termination for incoming and outgoing calls’ during the four-month period when the string of robberies occurred.”120Id. Between the two orders, “the Government obtained 12,898 location points cataloging Carpenter’s movements—an average of 101 data points per day.”121Id.

Prosecutors charged Carpenter with “six counts of robbery and an additional six counts of carrying a firearm during a federal crime of violence.”122Id. Carpenter argued in a pre-trial motion that the CSLI evidence should be suppressed: “the Government’s seizure of the records violated the Fourth Amendment because they had been obtained without a warrant supported by probable cause,” but his motion was denied.123Id. At trial, an expert witness from the FBI testified about CSLI, explaining that “each time a cell phone taps into the wireless network, the carrier logs a time-stamped record of the cell site and particular sector that were used.”124Carpenter, 138 S. Ct. at 2212. Using CSLI, the expert witness “produced maps that placed Carpenter’s phone near four of the charged robberies.”125Id. at 2213. The government leaned on the CSLI information in its closing argument, and a jury convicted Carpenter of “all but one of the firearm counts,” resulting in a sentence of “more than 100 years in prison.”126See id. (“In the Government’s view, the location records clinched the case: They confirmed that Carpenter was ‘right where the . . . robbery was at the exact time of the robbery.’”).

The Sixth Circuit Court of Appeals affirmed, concluding “that Smith controlled and that Carpenter had no Fourth Amendment right to his CSLI,”127Ormerod & Trautman, supra note 15, at 129 (citing Carpenter, 819 F.3d at 887). noting that “courts have not (yet, at least) extended [Fourth Amendment] protections to the internet analogue to envelope markings, namely the metadata used to route internet communications, like sender and recipient addresses on an email, or IP addresses.”128Id. (alteration in original) (quoting Carpenter, 819 F.3d at 887).

2.     Justice Roberts’s Majority Opinion

While Justice Roberts’s “wide-ranging” opinion applying the Katz “reasonable expectation of privacy” framework makes it difficult to identify precisely what constitutes the Carpenter test,129See, e.g., Ohm, supra note 73, at 370 (noting that “[d]ifferent characteristics of CSLI data and smartphone use are emphasized throughout Chief Justice Roberts’s opinion”). Roberts identified three factors supporting the Court’s conclusion that “the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection”: (1) the “deeply revealing nature of CSLI”; (2) “its depth, breadth, and comprehensive reach”; and (3) “the inescapable and automatic nature of its collection.”130Carpenter, 138 S. Ct. at 2223.

The Court analogized to an ankle monitor to describe the government’s CSLI tracking, but it also noted that—unlike with other forms of surveillance—CSLI allows the government to “travel back in time to retrace a person’s whereabouts.”131Id. at 2218. Trevor Burrus and James Knight of the Cato Institute observed that due to “the increased privacy interest and the decreased degree of third-party sharing, Roberts came to the ‘narrow’ holding that cell phone location data is a special case worthy of special protection, and thus the government must obtain a warrant for CSLI in most cases.”132Burrus & Knight, supra note 21, at 89.

3.     Justice Kennedy, Justice Thomas, and Justice Alito’s Dissents

Justice Kennedy’s dissent, joined by Justice Thomas and Justice Alito, applied the Katz framework but “came to the opposite conclusion”—that “there is no reasonable expectation of privacy in the data because the cell-site location records are created and controlled by providers ‘which aggregate and sell this information to third parties,’ and because users voluntarily share location data for other purposes.”133See Teachout, supra note 114, at 106 (citing Carpenter, 138 S. Ct. at 2229–30, 2232 (Kennedy, J., dissenting)).

In his dissent, Justice Thomas articulated what has been called a “stridently originalist position against Katz, the test of which he said ‘has no basis in the text or history of the Fourth Amendment.’”134Id. (citing Carpenter, 138 S. Ct. at 2236 (Thomas, J., dissenting)); see also Burrus & Knight, supra note 21, at 90 (“Although Justice Thomas joined Justice Kennedy’s dissent, agreeing that Supreme Court precedent would dictate the result Kennedy advocated, he separately argued that the entire Katz doctrine should be overruled and the Court should return to a more originalist, textualist, and property-based interpretation of the Fourth Amendment.”). Justice Thomas argued that the Katz test, in addition to departing from the text of the Fourth Amendment, has proved unworkable in practice.135Carpenter, 138 S. Ct. at 2244 (Thomas, J., dissenting) (observing that “[e]ven Justice Harlan, four years after penning his concurrence in Katz, confessed that the test encouraged ‘the substitution of words for analysis’” (quoting United States v. White, 401 U.S. 745, 786 (1971) (Harlan, J., dissenting))). He further argued that the case should turn not on “whether a search occurred,” but rather “on whoseproperty was searched,” concluding that “[b]y obtaining the cell-site records . . . the Government did not search Carpenter’s property.”136Id. at 2235 (Thomas, J., dissenting) (“He [Carpenter] did not create the records, he does not maintain them, he cannot control them, and he cannot destroy them. Neither the terms of his contracts nor any provision of law makes the records his. The records belong to [the cell phone service providers].”).

Justice Alito’s dissent, joined by Justice Thomas, also took on what has been called a “strident originalist position,” but unlike Justice Thomas, Justice Alito “focused on attacking the idea that a subpoena may be a search (while agreeing that the cell-site data was not Carpenter’s property).”137See Teachout, supra note 114, at 107 (citing Carpenter, 138 S. Ct. at 2247 (Alito, J., dissenting)). Justice Alito argued first that the majority “ignore[d] the basic distinction between an actual search . . . and an order merely requiring a party to look through its own records and produce specified documents.”138Carpenter, 138 S. Ct. at 2247 (Alito, J., dissenting). Second, Justice Alito pointed out that it was “revolutionary” that the majority “allow[ed] a defendant to object to the search of a third party’s property,” which “flouts the clear text of the Fourth Amendment” and “cannot be defended under either a property-based interpretation of that Amendment or our decisions applying the reasonable-expectations-of-privacy test adopted in Katz.”139Id. at 2247, 2257.

4.     Justice Gorsuch’s Dissent

Some commentators regard Justice Gorsuch’s dissent as the most interesting and possibly the most significant opinion in the case.140See, e.g., Jordan M. Blanke, Carpenter v. United States Begs for Action, 2018 U. Ill. L. Rev. Online 260, 262 (2018); Burrus & Knight, supra note 21, at 80 (“Justice Gorsuch’s dissent in particular reads like the opening salvo in what will likely be a career-long attempt to re-work the Court’s Fourth Amendment jurisprudence.”); see also Donohue, supranote 10, at 389 (arguing that the Court should follow Gorsuch’s property-rights approach). Highly critical of the third-party doctrine,141See Carpenter, 138 S. Ct. at 2262 (Gorsuch, J., dissenting) (“What’s left of the Fourth Amendment?”). Justice Gorsuch outlined three possible directions the Court could take in the future to address the problem posed by the Court’s precedents: (1) “ignore the problem, maintain Smith and Miller, and live with the consequences”; (2) “set Smith and Miller aside and try again using the Katz ‘reasonable expectation of privacy’ jurisprudence that produced them”; and (3) “look for answers elsewhere.”142Id.

Regarding the first option, Justice Gorsuch concluded that Smith and Miller were a “doubtful application of Katz that lets the government search almost whatever it wants whenever it wants.”143Id. at 2264. Similarly, he concluded that the second option “inevitably leads” to “two amorphous balancing tests, a series of weighty and incommensurable principles to consider in them, and a few illustrative examples that seem little more than the product of judicial intuition.”144Id. at 2267.

In the remainder of his dissent, Justice Gorsuch argued for option three, stating that “[t]here is another way”—namely, the traditional pre-Katz approach, which asked simply “if a house, paper, or effect was yours under law.”145Id. at 2267–68. While Justice Gorsuch acknowledged that he did “not begin to claim all the answers today” and that “much work is needed to revitalize this area,” he did claim to “have a pretty good idea what the questions are,” including “what kind of legal interest is sufficient to make something yours?146Id. at 2268. And what source of law determines that?”147Carpenter, 138 S. Ct. at 2268 (Gorsuch, J., dissenting). Justice Gorsuch observed that “[u]nder this more traditional approach, Fourth Amendment protections for your papers and effects do not automatically disappear just because you share them with third parties.”148Id.

Justice Gorsuch offered five thoughts to start the discussion: First, he argued that “the fact that a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them.”149Id. Second, he doubted “that complete ownership or exclusive control of property is always a necessary condition to the assertion of a Fourth Amendment right.”150Id. at 2269. Third, he argued that “positive law may help provide detailed guidance on evolving technologies without resort to judicial intuition.”151Id. at 2270. Fourth, he cited Ex parte Jackson and argued for the “existence of a constitutional floor below which Fourth Amendment rights may not descend,” observing that “while positive law may help establish a person’s Fourth Amendment interest there may be some circumstances where positive law cannot be used to defeat it.”152Id. Lastly, he suggested that “this constitutional floor may, in some instances, bar efforts to circumvent the Fourth Amendment’s protection through the use of subpoenas.”153Carpenter, 138 S. Ct. at 2271 (Gorsuch, J., dissenting).

Justice Gorsuch expressed concerns about the ramifications of the majority’s decision to “keep Smith and Miller on life support and supplement them with a new and multilayered inquiry that seems to be only Katz-squared,” which he worried would result in “more trouble than help.”154Id. at 2272. Professor Donohue echoes Justice Gorsuch’s concerns, arguing that even as the majority opinion “declared the warrantless search of CSLI unreasonable, it introduced myriad questions that will push the lower courts into uncharted territory.”155See Donohue, supra note 10, at 352 ( “Without clear direction, the decision is likely to lead to further chaos, fragmentation in the circuits, and reversals in the courts of appeals—far from the predictability and certainty essential to rule of law.”). Justice Gorsuch concluded his dissent by calling for further development of the traditional Fourth Amendment approach in future cases, observing that Carpenteroffers a “cautionary example” of what happens when the traditional approach goes unexplored.156Carpenter, 138 S. Ct. at 2272 (Gorsuch, J., dissenting).

II.     How Can Bailment Doctrine Help?

The focus of this Part is how the “ancient principle”157Id. at 2269. that a bailee is strictly liable for conversion for misdelivery of a bailment supports Justice Gorsuch’s first point—that just because “a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them.”158Id. at 2268.

This Part first agrees with Professor Donohue’s suggestion that the rule of functional equivalence could help identify when digital records (such as CSLI) are modern-day “papers and effects” warranting Fourth Amendment protection. Second, assuming that CSLI should be treated in the same way as “papers and effects,” this Part explores how bailment doctrine—specifically liability for conversion for misdelivery by a bailee—supports Justice Gorsuch’s critique of the third-party doctrine.159Id. This Part concludes by providing an example of how bailment principles could be applied to facts like those in Carpenter.160The Supreme Court’s narrow decision in Carpenter leaves untouched—for now—other key aspects of government surveillance or data collection, such as stingrays, cell tower dumps, security cameras, and national security data collection. For an examination of how Carpenter could apply in those contexts, see Rick Aldrich, Privacy’s Third-Party Doctrine: Initial Developments in the Wake of Carpenter, 15 Scitech Law. 5 (2019).

A.     Digital Records as “Papers and Effects”

Before addressing Justice Gorsuch’s point about retaining an interest in information shared with a third party, it is necessary to determine whether digital records like CSLI are to be considered modern-day “papers and effects.” Justice Gorsuch’s dissent asks the question “what kind of legal interest is sufficient to make something yours?” and suggests one possible answer is “the common law . . . extended by analogy to modern times.”161Carpenter, 138 S. Ct. at 2268 (Gorsuch, J., dissenting).

Similarly, Professor Donohue suggests that to determine ownership of digital records, the Court could adopt a “but for analysis” by looking at “whether the material would exist but for the right-holder’s actions.”162Donohue, supra note 10, at 353. Donohue argues that with CSLI, it is up to the person who “buys the phone, charges it, turns it on, and decides when and where to carry it” to determine where records of the person’s phone use—including location information—are shared.163Id. Donohue also argues for a “functional equivalence” approach to papers and effects, citing Professor Paul Ohm’s syllogism defining “technological equivalence”:

The Court in the past has held that information in a particular, traditional privacy context is protected by the Fourth Amendment. A technology produces information that is a modern-day equivalent to the information produced in the traditional context of step one. The information in the modern context is also protected by the Fourth Amendment.164Id. at 386–87 n.193 (quoting Ohm, supra note 73, at 394).

Donohue argues that the Court can apply the same rule of functional equivalence to papers as it has in other contexts. Because an individual can have an “ownership interest” in digital records, Donohue suggests that it is up to that individual “to determine with whom the information generated by them is shared,” and thus “that person holds the original right.” 390–91.

Justice Gorsuch offered a similar observation regarding CSLI: because customers have certain rights regarding their data, and carriers are forbidden to take certain actions, then “[p]lainly, customers have substantial legal interests in this information, including at least some right to include, exclude, and control its use.”166Carpenter, 138 S. Ct. at 2272 (Gorsuch, J., dissenting). Justice Gorsuch suggested that “[t]hose interests might even rise to the level of a property right.”167Id.

B.     How Principles of Bailment Law Relate to the Fourth Amendment

Assuming Professor Donohue and Justice Gorsuch are correct that digital records such as CSLI should be treated the same way as “papers and effects,” the “ancient principles”168Id. at 2269. of bailment law shed light on what happens when those records are shared with a third party. Specifically, the rule that a bailee is strictly liable for conversion for misdelivery of a bailment supports Justice Gorsuch’s proposition that just because “a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them.”169Id. at 2268. Application of the bailment rule regarding conversion for misdelivery undercuts the very premise of the third-party doctrine—contradicting the holding from Smith that “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties.”170Smith v. Maryland, 442 U.S. 735, 743–44 (1979).

1.     Bailment Doctrine Generally

In essence, a bailment is a “delivery of personal property by one person (the bailor) to another (the bailee) who holds the property for a certain purpose.”171Bailment, Black’s Law Dictionary (11th ed. 2019). Bailments can be constructive, sometimes called “implied-in-law bailments,” which can “occur even in the absence of the voluntary delivery and acceptance of the property that is usually necessary to create a bailment relationship.”1728A Am. Jur. 2d Bailments § 12 (2019). Furthermore, general rules of liability govern the bailor-bailee relationship, even in the absence of any special contract.173Id. § 77. With these general principles established, the rule regarding misdelivery is examined below.

2.     Strict Liability for Conversion for a Bailee’s Misdelivery

The vast majority of jurisdictions follow the general rule that any delivery of property by a bailee to someone not authorized to receive it constitutes conversion, for which the bailee is strictly liable.174See, e.g., Fireman’s Fund Ins. Co. v. Wagner Fur, Inc., 760 F. Supp. 1101, 1106 (S.D.N.Y. 1991) (applying New York law and holding that “like any other bailee, a common carrier is liable for conversion if it misdelivers property, even by innocent mistake”); Hall v. Bos. & Worcester R.R., 96 Mass. 439, 443 (1867) (holding that “a delivery to an unauthorized person is as much a conversion as would be a sale of the property, or an appropriation of it to the bailee’s own use”). For a list of cases representing the general support across a majority of jurisdictions for the rule that a bailee is strictly liable for conversion for misdelivery of a bailment, see infra Appendix. This holds true even if the bailee acts innocently or by mistake and regardless of the nature of the bailment.175See, e.g., Byer v. Canadian Bank of Com., 65 P.2d 67, 68 (Cal. 1937) (holding that misdelivery of bailed goods imposes liability upon the bailee even where the bailee acted innocently and by mistake); see also 8A Am. Jur. 2d Bailments § 73 (2019) (“[A] delivery to an unauthorized person is as much a conversion as a sale of the property or an appropriation of it to the bailee’s own use would be, and neither a sincere and apparently well-founded belief that the tortious act was right, nor the exercise of any degree of care, constitutes a defense.”); Restatement (Second) of Torts § 234 (1965) (“A bailee . . . who makes an unauthorized delivery of a chattel is subject to liability for conversion to his bailor . . . unless he delivers to one who is entitled to immediate possession of the chattel.”). The theory behind this general rule is that a bailee’s unauthorized transfer of the bailment is “an ‘exercise of ownership, dominion and control’ inconsistent with the bailor’s rights, and thus constitutes a conversion.”176Fotos v Firemen’s Insurance Co., 533 A.2d 1264, 1267 (D.C. App. 1987)(citing Lipman v Petersen, 575 P.2d 19, 21 (Kan. 1978)). Thus “misdelivery” simply means any delivery to a person not authorized by the bailor to receive the bailment.177See, e.g., 8A Am. Jur. 2d Bailments § 133.

This rule of bailment is consistent with existing Supreme Court case law. For example, as Justice Gorsuch pointed out in Carpenter, in Ex parte Jackson, the “Court held that sealed letters placed in the mail are ‘as fully guarded from examination and inspection, except as to their outward form and weight, as if they were retained by the parties forwarding them in their own domiciles.’”178Carpenter v. United States, 138 S. Ct. 2206, 2269 (2018) (Gorsuch, J., dissenting) (quoting Ex parte Jackson, 96 U.S. 727, 733 (1878)). According to Justice Gorsuch, it did not matter that the letters were “bailed” to the government as a third party—“[t]he sender enjoyed the same Fourth Amendment protection as he does ‘when papers are subjected to search in one’s own household.’”179Id. (quoting Jackson, 96 U.S. at 733).

C.     Applying Bailment Law to Facts Like Those in Carpenter

Justice Gorsuch concluded his dissent by criticizing litigants, including Mr. Carpenter, for not raising arguments based on property or common law, warning that “[t]hese omissions do not serve the development of a sound or fully protective Fourth Amendment jurisprudence.”180Id. at 2272. Justice Gorsuch observed that cases like United States v. Jones in 2012 and Florida v. Jardines181565 U.S. 1104 (2012). in 2013 should have put litigants on notice that “arguments like these may vindicate Fourth Amendment interests even where Katz arguments do not.”182Carpenter, 138 S. Ct. at 2272. How should a litigant in a similar case present an argument based on the type of traditional, property-based framework that Justice Gorsuch suggests?

The first step could be to argue that the digital record at issue is the modern-day equivalent of a “paper or effect,” perhaps by adopting Professor Donohue’s “but for” test and arguing that the record was created solely as a result of the person’s actions.183See Donohue, supra note 10, at 353. In the case of CSLI, as already noted, the data is only gathered by the phone company as a result of actions the litigant took—whether through calls, texts, or data connections.184See Carpenter, 138 S. Ct. at 2220 (“Virtually any activity on the phone generates CSLI, including incoming calls, texts, or e-mails and countless other data connections that a phone automatically makes when checking for news, weather, or social media updates.”). Given the vast amount of information that metadata collection can reveal, a litigant could also argue for the application of “functional equivalence” to the digital records, reasoning that the metadata collection revealed information that would have been contained in the person’s “house, papers, or effects” during the Founding era.185Donohue, supra note 10, at 386.

After establishing that the digital record in question is a modern-day “paper or effect,” the second step is to argue that bailment principles so undercut the underlying premise of the third-party doctrine that the third-party doctrine should be formally abolished.186See Carpenter, 138 S. Ct. at 2220 (noting that the majority opinion did not “disturb the application of Smith and Miller”). Because any unauthorized transfer of the bailment (here, the digital record) to a third party would render the record holder strictly liable for conversion under a bailment analysis, a litigant could argue that he did not give up a property right in the record just because the company now holds the information as a bailee. Were a court to agree with this type of argument, the government must then obtain a warrant before acquiring digital records, such as CSLI, as the records would constitute someone’s “papers or effects.”


If a digital record such as CSLI—that would not have been produced but for a person’s actions—is considered to be the modern-day equivalent of that person’s “papers or effects,” bailment law could be applied to indicate that any unauthorized disclosure of that record to a third party (i.e., law enforcement) is a conversion for which the record-holding company is strictly liable. Thus, under a traditional property-based framework, which simply “asked if a house, paper, or effect was yours under law,”187Id. at 2267–68 (Gorsuch, J., dissenting). Fourth Amendment protections would be triggered and the government must get a warrant to obtain the record. Alternatively, under a Katz analysis, just because a person voluntarily submitted information in a digital record to a third party does not mean that the person has yielded their “reasonable expectation of privacy” in the record. Viewed under a bailment lens, an expectation exists that a bailee will not deliver a digital record—a modern-day “paper or effect”—to an unauthorized party. And the fact that a bailee would be held strictly liable for such a misdelivery indicates that society views the expectation as reasonable. Under either analysis, the rule that a bailee is liable for conversion for misdelivery could help end the third-party doctrine exception and strengthen Fourth Amendment protections of digital records.

 Appendix: Support for the General Rule Regarding Conversion for Misdelivery of a Bailment

The cases in the table below represent most states’ general support for the rule that a bailee is strictly liable for conversion for misdelivery of a bailment. The cases listed range from 1790 to as recent as 2004, illustrating the long history of the rule.


Case Citation

Alabama S/M Indus., Inc. v. Hapag-Lloyd A.G., 586 So. 2d 876 (Ala. 1991)
Alaska Thompson v. Anderson, 824 P.2d 712, 715 (Alaska 1992)
Arizona Lerner v. Brettschneider, 598 P.2d 515, 517 (Az. Ct. App. 1979)
Arkansas Little Rock, Miss. River & Tex. Ry. Co. v. Glidewell, 39 Ark. 487, 490 (1882)
California Byer v. Canadian Bank of Com., 65 P.2d 67, 68 (Cal. 1937)
Colorado Dean Witter Reynolds Inc. v. Variable Annuity Life Ins. Co., 373 F.3d 1100, 1106 (10th Cir. 2004)
Connecticut Griswold v. Judd, 1 Root 221, 221 (Conn. Super. Ct. 1790)
District of Columbia Fotos v Firemen’s Ins. Co., 533 A.2d 1264 (D.C. App. 1987)
Florida Star Fruit Co. v. Eagle Lake Growers, 33 So. 2d 858, 860 (Fla. 1948)
Georgia Darling v. Purdom, 81 S.E. 800, 801 (Ga. 1914)
Idaho Quinto v. Millwood Forest Prods., Inc., 938 P.2d 189, 192 (Idaho Ct. App. 1997)
Illinois Dolphin v. Davis, 183 Ill. App. 118, 120 (1913)
Indiana Inland Metals Ref. Co. v. Ceres Marine Terminals, Inc., 557 F. Supp. 344, 348 (N.D. Ill. 1983) (applying Indiana law); Sullivan & O’Brien v. Kennedy, 25 N.E.2d 267, 268 (Ind. App. 1940)
Kansas Lipman v. Petersen, 575 P.2d 19 (Kan. 1978)
Kentucky Kierce’s Adm’r v. Farmers’ Bank, 191 S.W. 644, 647 (Ky. 1917)
Massachusetts Hall v. Bos. & Worcester R.R., 96 Mass. 439, 439 (Mass. 1867)
Michigan Gen. Exch. Ins. Corp. v. Serv. Parking Grounds, 235 N.W. 898, 900 (Mich. 1931)
Minnesota Hildegarde, Inc. v. Wright, 70 N.W.2d 257, 260 (Minn. 1955)
Mississippi Edwards Hotel Co. v. Terry, 187 So. 518, 522 (Miss. 1939)
Missouri Motors Ins. Corp. v. Union Mkt. Garage, 207 S.W.2d 836, 838 (Mo. App. 1948)
Nebraska Zimmerman v. FirsTier Bank, N.A., 585 N.W.2d 445, 453 (Neb. 1998)
New Jersey Reinfeld, Inc. v. Griswold & Bateman Warehouse Co., 458 A.2d 1341, 1344 (N.J. Super. Ct. Law. Div. 1983)
New Mexico Veterinary Pharm., Inc. v. Pugliese, Civ. No. 03-00838 MV/LCS, 2005 WL 8163653, at *7 (D.N.M. Sept. 28, 2005)
New York Fireman’s Fund Ins. Co. v. Wagner Fur, Inc., 760 F. Supp. 1101, 1106 (S.D.N.Y. 1991)
North Carolina Esteel Co. v. Goodman, 348 S.E.2d 153, 157 (N.C. Ct. App. 1986)
Ohio Aetna Cas. & Sur. Co. v. Higbee Co., 76 N.E.2d 404, 409 (Ohio Ct. App. 1947)
Oklahoma Delong v. Mason, 83 P.2d 547, 549 (Okla. 1938)
Oregon Atlas Hotel Supply Co. v. Baney, 543 P.2d 289, 292 (Or. 1975)
Pennsylvania Shenk v. Phila. Steam Propeller Co., 60 Pa. 109, 116 (Pa. 1869)
Rhode Island Lowney v. Knott, 120 A.2d 552, 554 (R.I. 1956)
South Carolina Marlow v. Conway Iron Works, 125 S.E. 569, 571 (S.C. 1924)
South Dakota Rensch v. Riddle’s Diamonds of Rapid City, Inc., 393 N.W.2d 269, 272 (S.D. 1986)
Tennessee Dispeker v. New S. Hotel Co., 373 S.W.2d 904, 910 (Tenn. 1963)
Texas Cent. Meat Mkt. v. Longwell’s Transfer, 62 S.W.2d 87, 89 (Tex. Comm’n App. 1933)
Utah Christensen v. Pugh, 36 P.2d 100, 103 (Utah 1934)
Vermont Winslow, Ward & Co. v. Vermont & M.R. Co., 42 Vt. 700, 704 (Vt. 1870)
Virginia Ry. Exp. Agency v. Kessler, 52 S.E.2d 102, 103 (Va. 1949)
West Virginia Dudley v. Chicago, M. & St. P. Ry. Co., 52 S.E. 718, 719 (W. Va. 1906)
Wisconsin Rowlands v. Elec. Constr. Co., 182 N.W. 736, 738 (Wis. 1921)



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