On June 22, 2018, the Supreme Court of the United States released the 5-4 opinion in Carpenter v United States, 585 US _ (2018) holding that a warrant is required for law enforcement to obtain cell site location information (CSLI) from a wireless carrier. “Given the unique nature of cell phone location records,” wrote Chief Justice John Roberts, “the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection.” He was joined by Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan. In dissent, Justices Anthony Kennedy, Clarence Thomas, Samuel A. Alito and Neil Gorsuch wrote separate opinions.

1. Introduction

Cell site location information is geolocation data generated by a cell phone’s communication with cell towers that are intentional and automatic. Intentional actions include simply turning the phone on causing it to communicate with the nearest cell tower. Other actions are placing a phone call and sending a text message. Automatic actions include receiving a text message or when the phone sends a periodic update to the network. The greater the concentration of cell towers in a geographic area, the more precise the location information will be. (See: Sabrina McCubbin. Summary: The Supreme Court Rules in Carpenter v. United States. Lawfare. June 22, 2018)

I discussed Carpenter in previous posts to On The Wire so I will only review the facts briefly. In 2011 four men were arrested following an FBI investigation into a series of armed robberies of Radio Shack and T-Mobile stores in Detroit, Michigan. One of the men confessed. He gave his cell phone number and the cell phone numbers of others involved to investigators. The police obtained orders for the production of “transactional records” including cell site location information under the Stored Communications Act, 18 USC s 2703(d). Three magistrate judges found that the standard of suspicion under the statute had been met. Timothy Carpenter’s records were included. (See: On The Wire. Digital Crumbs. May 26, 2017; and, Proxy Tracking. August 12, 2017)

2. Three Takeaways

The only way to avoid creating cell phone geolocation data would be to live as a digital hermit. In recognition of the ubiquity of cell phones in the information age, Chief Justice Roberts described the question presented as a “new phenomenon” – the ability to chronicle a person’s past movements by cell phone location data that is “detailed, encyclopedic, and effortlessly compiled”. Although the majority does not expressly adopt the mosaic theory of the Fourth Amendment, it is implicit in the court’s language. As Chief Justice Roberts said, “[T]his case is not about ‘using a phone’ or a person’s movement at a particular time. It is about a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years.” Privacy rights were thus implicated far beyond Smith v Maryland, 442 US 735 (1979) [outgoing call data] and United States v Miller, 425 US 435 (1976) [bank records]. (slip op., pp 10, 17)

I will condense three takeaways from the opinion that may influence Fourth Amendment analysis of other emerging technologies.

(a) Mosaic Theory

A cell phone “faithfully follows its owner beyond public thoroughfares into private residences, doctor’s offices, political headquarters, and other potentially revealing locales”. When the Government tracks the location of a cell phone it “achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user”. The retrospective quality of the data gives law enforcement access to “a category of information otherwise unknowable”. The Government can now “travel back in time” to retrace a person’s whereabouts subject only to the retention policies of wireless carriers. What Chief Justice Roberts is really talking about here is the mosaic theory – not only the retracing of a person’s whereabouts but the drawing of inferences about who they are from where they’ve been.

Cell site location information does not distinguish between targets of law enforcement and those who are not suspected of any crime. The data is collected indiscriminately. Everyone is tracked because location data is continually logged for all of the 400 million devices in the United States. Whoever the suspect may turn out to be – he would have been “tailed” every moment of every day for five years. “Only the few without cell phones,” wrote Chief Justice Roberts, “could escape this tireless and absolute surveillance.” The new phenomenon then, this chronicle of our past, raised dual aspects of the mosaic theory – quantity of data and quality of content. (slip op., pp 13-14) (See: On The Wire. Proxy Tracking. August 12, 2017; and, Constructing Mosaics. December 16, 2017)

(b) Fourth Amendment

Chief Justice Roberts emphasized that the basic purpose of the Fourth Amendment is to “safeguard the privacy and security of individuals against arbitrary invasions by government officials”. Camara v Municipal Court of City and County of San Francisco, 387 US 523, 528 (1967). The jurisprudence has recognized two basic guideposts. First, the Fourth Amendment seeks to secure “the privacies of life” against “arbitrary power”. Boyd v United States, 116 US 616, 630 (1886). Second, a certain aim of the Framers was “to place obstacles in the way of a too permeating police surveillance”. United States v Di Re, 332 US 581, 595 (1948).

The majority opinion keeps “this attention to Founding-era understandings in mind when applying the Fourth Amendment to innovations in surveillance tools. As technology has enhanced the Government’s capacity to encroach upon areas normally guarded from inquisitive eyes, this Court has sought to ‘assure [ ] preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.’ Kyllo v United States, 533 US 27, 34 (2001). Whether the Government employs its own surveillance technology [ ] or leverages the technology of a wireless carrier, we hold that an individual maintains a legitimate expectation of privacy in the record of his physical movements.” (slip op., pp 4-6, 11)

(c) Third Party Doctrine

The Government’s primary argument was that cell-site records are “fair game” because they are business records created and maintained by wireless carriers. But the Government’s position failed to contend with the “seismic shifts in digital technology” that made possible the tracking of not only Carpenter’s location but everyone else’s – and not for a short period but for years. “There is a world of difference,” Chief Justice Roberts wrote, “between the limited types of personal information addressed in Smith [outgoing call data] and Miller [banking records] and the exhaustive chronicle of location information casually collected by wireless carriers today.”

The third-party doctrine partly stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another. But, as the majority held, the fact of “diminished privacy interests does not mean that the Fourth Amendment falls out of the picture entirely”. Apart from disconnecting the phone from the network, there is no way to avoid creating a trail of location data. As a result, “in no meaningful sense does the user voluntarily ‘assume[ ] the risk’ of turning over a comprehensive dossier of his physical movements”. (slip op., pp 15-7)

3. Stored Communications Act

What, then, about the orders under the Stored Communications Act? As I mentioned, the cell site records were obtained by orders granted by magistrate judges that required the police to establish “reasonable grounds” for believing that the records were “relevant and material to an ongoing investigation”. That standard fell short of probable cause for a warrant and the requirement of “individualized suspicion” before a search and seizure may take place. Under the standard in the statute, the police only had to show that the cell site data might be pertinent to an ongoing investigation – a departure from the probable cause rule. Therefore, the orders under s 2703(d) were not valid instruments for accessing the historical data. “Before compelling a wireless carrier to turn over a subscriber’s CSLI,” Chief Justice Roberts held, “the Government’s obligation is a familiar one – get a warrant.” (slip op., p 19)

4. What Carpenter Did Not Do

It is important to emphasize what Carpenter did not do. First, the ruling does not change the case-specific exceptions such as when “the exigencies of the situation” make the needs of law enforcement so compelling that a warrantless search is objectively reasonable under the Fourth Amendment. These exigencies include “the need to pursue a fleeing suspect, protect individuals who are threatened with imminent harm, or prevent the imminent destruction of evidence”. Kentucky v King, 563 US 452, 460 (2011). (slip op., pp 21-2)

Second, Chief Justice Roberts stated that it was not necessary to decide whether there is a limited period for which the Government may obtain geolocation data free from Fourth Amendment scrutiny. “It is sufficient for our purposes today,” he wrote, “to hold that accessing seven days of CSLI constitutes a Fourth Amendment search”. The Chief Justice then went on to cast the decision as a “narrow one”. The majority expressly declined to comment on real time CSLI or tower dumps. The opinion does not address conventional surveillance tools such as security cameras. Nor does it consider other collection techniques involving foreign affairs or national security. Chief Justice Roberts cautioned, citing Justice Felix Frankfurter, that the court must tread carefully when considering new innovations to ensure that we do not “embarrass the future”. Northwest Airlines, Inc v Minnesota, 322 US 292, 300 (1944). (slip op., p 11, footnote 3, and pp 17-8)

5. Conclusion

In addition to the potential influence of the Carpenter ruling on Fourth Amendment scrutiny of other new technologies, the opinion may also impact the analysis of First Amendment rights. In a piece titled The Supreme Court Takes On the Police Use of Cellphone Records published in The New York Times edition of June 22, 2018, Alex Abdo of the Knight First Amendment Institute at Columbia University and Professor Kate Klonick of St. John’s Law School wrote:

“Imagine if the government had the power to force cellphone and internet providers to disclose the contact lists of journalists and their suspected sources, the names of protesters at a rally or the phone numbers and email addresses of everyone who contacted the author of a report critical of the government – all without a warrant. The rights of free speech, assembly and association secured by the First Amendment would be hollowed out by authority that expansive. Those are the real stakes of the Carpenter decision. While the court didn’t directly address these questions, it paved the way for their resolution, free from doctrinal anachronisms and sensitive to the threats to individual rights in the bold but scary world of modern technology.”