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  • Alex Raby

Supreme Court Extends Fourth Amendment Protection to Cell Phone Location Data

Updated: Oct 19, 2023

The Supreme Court ruled (by 5-4 majority decision) that the revealing nature of CSLI data invokes a “reasonable expectation of privacy” (within the meaning of Katz v. United States). The Supremes held that Cell Site Location Information (CSLI) has such a “comprehensive” and “revealing nature” that any examination of CSLI data by law enforcement amounts to SEARCH. (Carpenter v. United States, 138 S. Ct. 2206, 2223). Now law enforcement may only gain access to this information by way of a warrant, ordered by a neutral magistrate.

CSLI is information collected and compiled by cell phone service providers that reveals the location of a cell phone (to within a narrow geographic area) at a particular point in time. The data is collected automatically and continuously. Advances in technology now allow cell phone service providers to determine the location of a phone to within a very narrow geographic area (within feet in some instances). In contrast, now defunct versions of the same technology, CSLI data is collected in an automated fashion. Meaning that CSLI data is collected even when a cell phone is not being used. All that is required to collect the data is for the phone to be switched on. As a result, an examination of CSLI data can reveal a continuous log of a cell phone’s location and movements for as long as the data has been collected. Inevitably, given the fact that modern humans are invariably separated from their cellphones for very long, the data can be used to track an individual’s movements over a given time period.

While Carpenter v. United States now extends Fourth Amendment protection to CSLI data; not all Justices were satisfied with the decision. Justice Kennedy provided a dissenting opinion, in which Justices Thomas and Alito joined. Kennedy maintained that, as information freely exposed to service providers, the third party doctrine established in Smith and Miller applied. (arguing, therefore, that CSLI data may properly be obtained way of a subpoena, because under third party doctrine, data that has been voluntarily provided to a third party (for that party’s use or control) is not protected by the warrant requirement of the Fourth Amendment.

Justice Gorsuch also disagreed with the majority decision. In his stand-alone dissent Gorsuch argued the “reasonable expectations of privacy” doctrine, established by Katz and its progeny, is bad law and not necessary to protect privacy interests. Furthermore, Gorsuch argued that the third party doctrine established in Smith and Miller lies on a “faulty rationale.” (Carpenter v. United States, 138 S. Ct. 2206, 2272). And is, therefore, an equally inadequate lens through which to examine this case.

Smith and Miller established that a person can relinquish a privacy interest in “limited types of personal information” by voluntarily exposing that information to a third party (Carpenter v. United States, 138 S. Ct. 2206, 2219-2220). The problem with this law, Gorsuch argued, is that “people often doreasonably expect that information they entrust to third parties, especially information subject to confidentiality agreements, will be kept private.” Carpenter v. United States, 138 S. Ct. 2206, 2262-2263. Thus, the Third Party Doctrine rests on the “dubious proposition” that one can make objective statements about the subjective privacy expectations of each individual. Carpenter v. United States, 138 S. Ct. 2206, 2262-2263. Furthermore, Gorsuch continued, the majority cannot tell us whysomeone’s location when using a phone (Carpenter) is so much more sensitive than knowledge of who he was talking to (Smith), or what financial transactions he engaged in (Miller). Carpenter v. United States, 138 S. Ct. 2206, 2262-2263.

The Court has failed to produce a reliable principle by which this type of case can be determined. As a result, the available examples of the type of information that can be disclosed to a third party, but still maintain Fourth Amendment protection, are little more than the product of “judicial intuition.” Carpenter v. United States, 138 S. Ct. 2206, 2267. And, moreover, it is this key fact (in Gorsuch’s view) that puts the entire line of cases stemming from Katz at issue. For example, under Katz two essential elements must be shown to prove that information/data requires fourth amendment protection. First, an individual must demonstrate that efforts were made to maintain privacy. Second, (and this is the contentious part for Gorsuch) societymust be prepared to accept that particular privacy interest. Gorsuch argues that courts are notoriously bad at aligning their decisions with society’s expectations concerning privacy. Moreover, Gorsuch notes that the Supreme Court’s decisions are sometimes in direct opposition to what society, or large swathes of it, have expressed or demanded in their own legislation.

Gorsuch continued by levying a series of arguments against Katz and the “reasonable expectation of privacy” test. Noting, that both empirical and normative interpretation of the test is inadequate. Regarding an empirical interpretation, Gorsuch argues that it is unclear why Judges should be entrusted with conducting this test over legislators. Where legislators are better equipped to represent the views of their constituents, in contrast, judicial opinions often fail to reflect public views. Carpenter v. United States, 138 S. Ct. 2206, 2265. For example, Mincey v. Arizonainsists that the seriousness of the crime being investigated has no bearing on the level of Fourth Amendment protection deserved by the suspect. Carpenter v. United States, 138 S. Ct. 2206, 2265. However, Gorsuch points out, the work of scholars like Blumenthal, Adya, and Mogle suggests that the public, in fact, “are more tolerant of police intrusions” when they are investigating more serious crimes. Carpenter v. United States, 138 S. Ct. 2206, 2265. Regarding the normative approach, Gorsuch again asks why the judiciary and not the legislature gets to determine what society shouldbe prepared to accept as a reasonable expectation of privacy. Moreover, the “judicial intuition” that Katz requires the courts to engage in has “yielded an often unpredictable—and sometimes unbelievable—jurisprudence.” Carpenter v. United States, 138 S. Ct. 2206, 2266. On that note, Gorsuch had this to say:

Smith and Miller are only two examples; there are many others. Take Florida v. Riley, 488 U. S. 445, 109 S. Ct. 693, 102 L. Ed. 2d 835 (1989), which says that a police helicopter hovering 400 feet above a person’s property invades no reasonable expectation of privacy. Try that one out on your neighbors. Or California v. Greenwood, 486 U. S. 35, 108 S. Ct. 1625, 100 L. Ed. 2d 30 (1988), which holds that a person has no reasonable expectation of privacy in the garbage he puts out for collection. In that case, the Court said that the homeowners forfeited their privacy interests because “[i]t is common [**576] knowledge that plastic garbage bags left on or at the side of a public street are readily accessible to animals, children, scavengers, snoops, and other members of the public.” Id., at 40, 108 S. Ct. 1625, 100 L. Ed. 2d 30 (footnotes omitted). But the habits of raccoons don’t prove much about the habits of the country. I doubt, too, that most people spotting a neighbor rummaging through their garbage would think they lacked reasonable grounds to confront the rummager. Making the decision all the stranger, California state law expressly protected [***142] a homeowner’s property rights in discarded trash. Id., at 43, 108 S. Ct. 1625, 100 L. Ed. 2d 30. Yet rather than defer to that as evidence of the people’s habits and reasonable expectations of privacy, the Court substituted its own curious judgment.

Carpenter v. United States, 138 S. Ct. 2206, 2266

Gorsuch continued by making lengthy attacks on the current state of Fourth Amendment law, as well as potential remedies proposed by others; arguing that Katz, in combination with the third party doctrine, will continue to produce unpredictable results. He is convinced that the narrow decision provided in Carpenteris an inadequate solution; noting that the decision only leaves us “with two amorphous balancing tests, a series of weighty and in-commensurable principles to consider in them, and a few illustrative examples that seem little more than the product of judicial intuition.” Carpenter v. United States, 138 S. Ct. 2206, 2267 (2018).

As a proposed solution, Gorsuch argues for a return to a property-based approach to the warrant requirement of the Fourth Amendment. Noting that “reasonable expectations” under Katz may “supply one way to prove a Fourth Amendment interest”; however, they have “never been the only way.”

First, in defense of this approach, Gorsuch notes that looking to the property interests at play has long been the traditional way of resolving cases of this kind. Carpenter v. United States, 138 S. Ct. 2206, 2268-2272. Second, a property-centric approach allows individuals to disclose papers and effects (and data) to other people without automatically relinquishing their property (and privacy) rights. Carpenter v. United States, 138 S. Ct. 2206, 2268-2272. This approach has the benefit of embracing the fact that just because you have entrusted a third party with your data doesn’t mean you no longer wish that date to be kept private. Carpenter v. United States, 138 S. Ct. 2206, 2268-2272. Furthermore, this traditional approach, of looking to positive-law to determine privacy interests, may be invaluable when it comes to evolving technologies by negating the need to resort to judicial intuition. Carpenter v. United States, 138 S. Ct. 2206, 2269-2270 (2018). Law makers and courts around the United States are already starting to recognize and legislate the proprietary interests that one may hold in various forms of digital media. For example, the Texas Property Code defines “property” to include “property held in any digital or electronic medium.” Carpenter v. United States, 138 S. Ct. 2206, 2270 (2018). Furthermore, in Ajemian v. Yahoo!, is recognized that an e-mail account is a type of property often referred to as a ‘digital asset.’ 478 Mass. 169, 170 (2017). Thus, it is easy to see that “if state legislators or state courts say that a digital record has the attributes that normally make something property, that may supply a sounder basis for judicial decision making than judicial guesswork about societal expectations.” Carpenter v. United States, 138 S. Ct. 2206, 2270 (2018).

Carpenter v. United States is an illuminating opinion -- due in no small part -- to Justice Gorsuch’s dissenting opinion. While the dissent was compelling, Gorsuch’s arguments have yet to gain traction. (It is worth noting that the arguments he raised were in fact forfeit from the outset, as they were not raised by petitioner on appeal.) That being said Gorsuch rounded out the dissent with rather an optimistic tone; commenting that while the positive-law approach was waived in this instance, for others it may yet prove to be a “most promising line of argument.” Carpenter v. United States, 138 S. Ct. 2206, 2272 (2018).


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