While technology has empowered us to access a wealth of information about the world, it can also empower others to access a wealth of information about ourselves. When we feed personal information to our various electronic devices, can we expect that information to remain private?

The Supreme Court will hear arguments involving this question on Wednesday in Carpenter v. United States.[1] The Court will address whether the Fourth Amendment allows law enforcement to access the cell phone location data of individuals without a warrant. When cell phones connect with local cell towers, they leave a trail of data telling the service provider where the phone—and therefore, its owner—is at all times. In Carpenter, federal officials requested this information for petitioner Timothy Carpenter’s phone from his service providers, MetroPCS and Sprint, for a 127-day period. Under the current state of the law, they did not need a warrant.

Lower courts have held that acquiring cell site location information (CSLI) is not a search protected by the Fourth Amendment because the data comes from third parties who collect it in the ordinary course of business.[2] Under the so-called “third-party doctrine,” established in a pair of cases in the 1970s, the Supreme Court held that individuals have no reasonable expectation of privacy for information that they voluntarily convey to third parties. In United States v. Miller, authorities subpoenaed the defendant’s account records from his banks without a warrant.[3] The Court found that the subpoenas did not constitute a search: “the depositor takes the risk, in revealing his affairs to others, that the information will be conveyed by that person to the government.”[4]

Similarly, in Smith v. Maryland, the Court found that installing a device on a phone that tracks the numbers called was not a search.[5] According to the Court, reasonable people understand that the phone company has access to all numbers a phone has dialed, and so should have no expectation of privacy over them.[6] When the defendant tried to argue that his case was different because the phone company did not regularly keep active records of local calls, the Court declined to narrow Miller. Writing for the majority, Justice Blackmun refused to “make a crazy quilt of the Fourth Amendment,” instead relying on a bright-line third-party rule.[7] Thus, in an era before cell phones or the internet, the Court held that whenever people conveyed information that they reasonably expected could be obtained by a third party in the regular course of business, the government could acquire that information without a warrant.

More recently, however, the justices have acknowledged that technology has changed the landscape of Fourth Amendment protections. In Riley v. California, the Court unanimously found that the contents of an arrestee’s cell phone could not be searched without a warrant.[8] The state in Riley attempted to argue that precedent allowing law enforcement to search the body of an individual upon arrest applied.[9] Responding to the state’s analogy that searching a phone is like searching a bag, Chief Justice Roberts argued, “that is like saying a ride on horseback is materially indistinguishable from a flight to the moon.”[10]

In another unanimous decision, the Court in United States v. Jones held that attaching a GPS tracker to a person’s car constituted a search under the Fourth Amendment.[11] In a concurring opinion, Justice Sotomayor challenged the notion that people do not have a reasonable expectation of privacy over the “sum of [their] public movements,” made available by GPS monitoring, which can include those as personal as “trips to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on.”[12]

Justice Alito, also concurring, agreed that long-term monitoring of an individual’s location infringed on reasonable expectations of privacy.[13] Technology has now made relatively simple what previously would have required “a large team of agents, multiple vehicles, and perhaps aerial assistance.”[14]

The Court could rely on Jones and Riley to carve out an exception to the third-party doctrine for CSLI, recognizing its great potential for invasiveness. Based on Justice Sotomayor and Justice’s Alito’s opinions in Jones, the latter of which Justices Ginsburg, Breyer, and Kagan also joined, the Court appears likely to do so.

But it should go further, and abolish the third-party doctrine altogether. Rather than “make a crazy quilt of the Fourth Amendment,” the Court should recognize that no narrow list of exceptions can save the third-party doctrine in the 21st century.

We give a staggering amount of personal information to third parties, and not just our locations. Apple knows all of our contacts, calendars, reminders, and notes. Visa and Amazon know our purchasing habits, through which they also know what we read and watch. WebMD knows our physical and mental ailments. And of course, we share with Google our fears, biases, political leanings, sexual desires and frustrations, mental sufferings, body insecurities, addictions, obsessions, dreams, and aspirations. So much of our professional, social, emotional, and intellectual development takes place over the internet—all through our knowing reliance on a third party. Our Google search or web browser histories can probably tell more about ourselves than interviews with our best friends.

Rather than reasonably forsaking privacy through these third-party interactions, we often utilize them precisely because we seek additional privacy. We ask Google what we are afraid to ask anyone else. And we do so even though we know that somewhere the data is recorded—and, although unlikely, maybe even viewed by an actual human being—because we expect that nobody significant in our lives will see it, including the state.

Even before the digital era, the third-party doctrine was highly suspect. As Justice Marshall put it in his dissent in Smith: “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.”[15] He also recognized the practical necessity of involving third parties in our personal affairs, because of “the vital role that telephonic communication plays in our personal and professional relationships.”[16] One can only imagine what his reaction would be if he could see how we use our smartphones today.

The Fourth Amendment should revert to its traditional framework: reasonable expectations of privacy, regardless of whom we have actually shared our information with. Nobody would think it reasonable for the government to access our entire Google search history without a warrant, just as nobody would think it reasonable for the police to instantaneously learn everywhere we have been over the last 127 days.


[1] No. 16-402.

[2] See United States v. Carpenter, 819 F.3d 880, 888­–89 (6th Cir. 2016).

[3] 425 U.S. 435, 437 (1976).

[4] Id. at 443. The overarching standard for whether a state action is a search under the Fourth Amendment is whether it violates a person’s subjective and reasonable expectations of privacy. See Katz v. United States, 389 U.S. 347, 353 (1967).

[5] 442 U.S. 735, 742 (1979).

[6] Id.

[7] Id. at 745.

[8] 134 S. Ct. 2473 (2014).

[9] Id. at 2488

[10] Id.

[11] 565 U.S. 400 (2012).

[12] Id. at 415–416 (Sotomayor, J. concurring) (quoting People v. Weaver, 909 N.E.2d 1195, 1199 (N.Y. 2009)).

[13] Id. at 429–31 (Alito, J. concurring).

[14] Id. at 429.

[15] 442 U.S. at 749 (Marshall, J. dissenting).

[16] Id. at 751 (Marshall, J. dissenting).