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The decision in Miller was followed by Smith v. Maryland, 442 U.S. 735 (1979), in which the Court was called upon to decide whether law enforcement’s recording of phone numbers dialed on a landline phone was a search under the 4thAmendment.  The Court held it was not, because one doesn’t have a reasonable expectation of privacy in the numbers voluntarily dialed when it is common knowledge that the phone company kept a record of numbers dialed for a variety of business purposes. Once again, we run the risk that government agents will request those records from the phone company, so there is no issue with the government contemporaneously recording those dialed numbers.


The universe of electronic communication and data storage has changed much since Miller and Smith, and SCOTUS has tried to keep 4thAmendment jurisprudence relevant in a world that is probably beyond the imaginations of those living at the time the Bill of Rights was adopted. The ability to track the location of another is just the sort of technological advancement the Court has struggled with, deciding whether there is a reasonable expectation of privacy in one’s location. In general, it isn’t shocking to think that we have no protected privacy interest when we go out in public where we can be seen by anyone who cares to take a look at us.

But the ability of law enforcement to track our every movement, using our phones, is something altogether different. As Chief Justice Robert’s notes in Carpenter, several justices have already expressed concern over the growing ability to track a person’s movements, in real time or historically, using smartphone or GPS technology in United States v. Jones, 565 U.S. 400 (2012): “..five Justices agreed that related privacy concerns would be raised by, for example, ‘surreptitiously activating a stolen vehicle detection system’ in Jones's car to track Jones himself, or conducting GPS tracking of his cell phone. Id., at 426, 428 (ALITO, J., concurring in judgment); id., at 415 (SOTOMAYOR, J., concurring). Since GPS monitoring of a vehicle tracks ‘every movement’ a person makes in that vehicle, the concurring Justices concluded that ‘longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy’-regardless whether those movements were disclosed to the public at large. Id., at 430 (opinion of ALITO, J.); id., at 415 (opinion of SOTOMAYOR, J.).” Carpenter, 585 U.S. ___ (2018).


It is with that backdrop that the SCOTUS decided that we have a legitimate expectation of privacy in our CSLI data, but it is a narrow one. As a result, getting CSLI is a search and law enforcement must get a search warrant upon probable cause and may not rely on an order issued under the Stored Communications Act’s lesser standard.

The holding is grounded in part on the recognition of the extraordinary role that smartphones play in the lives of everyday Americans. Following a car on a public street is one thing, following one into the bathroom is entirely different; you can’t easily hide a car from public scrutiny, you should be able to hide other things you do even though your phone is in your back pocket. The nature of smartphones and how we use them means the government can now achieve near perfect surveillance, something that was unlikely if not impossible before now. “For that reason, ‘society's expectation has been that law enforcement agents and others would not- and indeed, in the main, simply could not-secretly monitor and catalogue every single movement of an individual's car for a very long period.’” Carpenter, 585 U.S. ___ (2018), quoting United States v. Jones, 565 U.S. 400, 430 (opinion of Alito, J.) (2012). As the opinion in Carpenter holds, “Allowing government access to cell-site records contravenes that expectation.”

The expectation of privacy holds even though the CSLI data is held by a third party. Invoking the third-party doctrine to justify a search for CSLI “fails to contend with the seismic shifts in digital technology that made possible the tracking of not only Carpenter's location but also everyone else's, not for a short period but for years and years. Sprint Corporation and its competitors are not your typical witnesses. Unlike the nosy neighbor who keeps an eye on comings and goings, they are ever alert, and their memory is nearly infallible. 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. The Government thus is not asking for a straightforward application of the third-party doctrine, but instead a significant extension of it to a distinct category of information.”

The second rationale for the third-party doctrine, that the information is voluntarily shared with that third-party, doesn’t change the calculus. The holding recognizes that cell phone users – that is, almost everyone in the nation – hardly share CSLI information in any understanding of the word. The Court notes that virtually every activity on the smartphone, whether the subscriber initiates that activity or the phone does it automatically, generates CSLI data. There is no way to avoid it, short of turning off the phone. “As a result, in no meaningful sense does the user voluntarily "assume [] the risk" of turning over a comprehensive dossier of his physical movements. Smith, 442 U.S., at 745.”  Carpenter,585 U.S. ___ (2018).


So, what can we make of this closely decided case? For one, the decision is explicitly a narrow one. Investigators who want to get historical CSLI data from cell service providers will need to get a search warrant. The holding does not address real-time tower dumps. It doesn’t impact traditional surveillance tools, like CCTV cameras. The holdings in Smith and Miller are left undisturbed, and it doesn’t address third-party business records that may incidentally reveal location data. In cold, practical terms, Carpenterholds that law enforcement must get a search warrant to get historical CSLI records; no more 2703(d) orders for those data.

Of course, CSLI is not the only kind of data collected by digital service providers. And the pace of technological innovation is such that the scope of the information collected and stored about us by digital service providers is going to increase, perhaps beyond our imagining. Carpenter is just the beginning. To me, it is a good one in that it recognizes that our world is vastly different than a generation ago, and that our concept of what should be “private” is changing. Recognizing that 4thAmendment jurisprudence should be informed by that dynamic of change is all to the good. 

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