Supreme Court: Warrant Now Required to Obtain Historical Cell Site Location Information

Womble Bond Dickinson

In a landmark 5–4 decision, the Supreme Court of the U.S. (Court) has reversed the decision of the U.S. Court of Appeals for the Sixth Circuit holding that generally, the government’s acquisition of historical cell site location information (CSLI) is a Fourth Amendment search that requires a warrant.1

Bottom Line: The Supreme Court’s decision dramatically expands the scope of the Fourth Amendment in an attempt to modernize it, and provides new safeguards to the right of privacy. The decision and dissents, with the exception of Chief Justice Roberts, reflect party lines with the majority opinion supported by Justices appointed by Democratic Presidents, and the dissents written by Justices appointed by Republican Presidents.  While the impact on Law Enforcement (LE) will be immediate, the potential impact on the private use of consumer data will likely invite future policy battles and litigation.


This case stems from the conviction of Timothy Carpenter of a series of robberies in Michigan and Detroit. In 2011, LE arrested four men suspected of robbing a series of Radio Shack and T-Mobile stores in Detroit, Michigan. One of the men confessed that a group of men had robbed nine different stores in Michigan and Ohio and identified accomplices and gave LE their cell phone numbers. Based on that information, prosecutors sought court orders under the Stored Communications Act to obtain the cell phone records for Timothy Carpenter and other suspects.2 Under that statute, the government must present specific and articulable facts showing that there are reasonable grounds to believe that the records sought are relevant and material to an ongoing criminal investigation. LE obtained two court orders directing Carpenter’s wireless carriers to disclose historical CSLI for Carpenter. The first order sought 152 days of CSLI records which produced 127 days of records and the second order requested seven days of CSLI which produced two days of records.

Carpenter was charged with six counts of robbery. Prior to trial, Carpenter moved to suppress the cell-site data provided by the wireless carriers, arguing that the government’s seizure of the records violated the Fourth Amendment because they had been obtained without a warrant supported by probable cause. LE argued that Carpenter lost his right to privacy in the CSLI because he voluntarily turned the records over to third parties. The lower district court denied Carpenter’s motion, and LE used the CSLI records to support a conviction showing Carpenter in the locations of the robberies at that time they occurred. Carpenter was convicted. The U.S. Court of Appeals for the Sixth Circuit affirmed the lower court holding, affirming that Carpenter lacked a reasonable expectation of privacy in the CSLI collected because he shared that information with his wireless carriers.3 Given that cell phone users voluntarily convey cell-site data to their carriers to establish communications, the Sixth Circuit concluded that under the third party doctrine, the CSLI amounted to business records not entitled to Fourth Amendment protection. The Supreme Court granted certiorari.

Majority Opinion

The Court framed the question presented as whether government conducts a search under the Fourth Amendment when it accesses historical CSLI records that provide a comprehensive chronicle of the user’s past movements. The Court’s answer, in an opinion authored by Chief Justice John Roberts, is that the government’s acquisition of Carpenter’s CSLI records was a Fourth Amendment search requiring a warrant. Justice Roberts explains that each time a phone connects to a cell site, it generates a time-stamped record known as CSLI which wireless carriers collect and store for their own business purposes. The Court explains that the history of the Fourth Amendment seeks to protect the rights of people to be secure in their person, houses, paper and effects, against unreasonable searches and seizures. According to the Court, the basic purpose of the Fourth Amendment is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials. While originally grounded in property rights, the Fourth Amendment protects not only property interests but certain expectations of privacy.4 When an individual seeks to preserve something as private, and this expectation of privacy is recognized by society as reasonable, the Court has held that government intrusion into that private sphere qualifies as a search and requires a warrant supported by probable cause.5

Although there is no definitive list of which expectations of privacy are entitled to protection, according to the Court, the analysis is informed by historical understandings of what was deemed an unreasonable search and seizure when the Fourth Amendment was adopted. The Court provides a framework with two basic principles: (1) the Amendment seeks to secure the privacies of life against arbitrary power;6 and (2) relatedly, a central aim of the Framers was to place obstacles in the way of too permeating police surveillance.7 As technology has enhanced the government’s capacity to encroach upon areas normally guarded, the Court has sought to assure preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.8

The Court claims that personal location information maintained by a third party does not fit neatly under existing precedent but lies at the intersection of two lines of cases. The first line addresses a person’s expectation of privacy in his physical location, and the second addresses a person’s expectation of privacy in information voluntarily turned over to third parties. Justice Roberts frames the issue as how to apply the Fourth Amendment to a new phenomenon: the ability to chronicle a person’s past movements through the record of his cell phone signals. Much like GPS tracking of a vehicle, CSLI is detailed and effortlessly compiled. At the same time, that the individual continuously reveals his location to his wireless carrier implicates the third party doctrine which holds where a person voluntarily provides information to a third party there is no expectation of privacy.

Expectation of Privacy in Physical Location
The Court states that it has already recognized that individuals have a reasonable expectation of privacy in the whole of their physical movements.9 The Court explains that society’s expectation has been that LE would not or simply could not, secretly monitor and catalogue every single movement of an individual’s car for a long period. In Kyllo, the Court rejected a mechanical interpretation of the Fourth Amendment and held that the use of a thermal imaging device to detect drugs from heat radiating inside a defendant’s home was tantamount to a search. Similarly, in Riley, recognizing the immense storage capacity of modern cell phones, the Court held that LE must generally obtain a warrant before searching the contents of a cell phone.10 In the GPS context, the Court held that the government’s installation of a GPS tracking device on a target's vehicle to monitor the vehicle's movements constitutes a search.

The Court asserts that allowing government access to CSLI records contravenes that expectation. Although CSLI records are generated for commercial purposes, according to the Court, that distinction does not negate Carpenter’s anticipation of privacy in his physical location. Here, mapping a cell phone’s location over the course of 127 days provides an all-encompassing record of the holder’s whereabouts. As with GPS information, the time stamped data provides an intimate window into a person’s life, revealing not only his particular movements, but through them his familial, political, professional, religious, and sexual associations.11 In short, Justice Roberts asserts that historical cell-site records present even greater privacy concerns than the GPS monitoring of a vehicle previously considered because 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. With access to CSLI, the government can travel back in time to retrace a person’s whereabouts, subject only to the retention polices of the wireless carriers, which the Court suggests is five years.12 Accordingly, the Court concludes that when the government accessed CSLI from the wireless carriers, it invaded Carpenter’s reasonable expectation of privacy in the whole of his physical movements.

Voluntary Disclosure to a Third Party
As to the voluntary disclosure to a third party, the Court states that it has drawn a line between what a person keeps private and what he shares with others, holding that a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties. Under the third party doctrine, the government is typically free to obtain shared information from the recipient without triggering Fourth Amendment protections. The third party doctrine is rooted in the Miller case where the Court rejected a Fourth Amendment challenge to the collection of bank records.13 The Court applied the same principles regarding information conveyed to a telephone company holding that the government’s use of a pen register that recorded outgoing phone numbers on a landline telephone was not a search.14 Noting the limited capabilities of pen registers, the Court concluded that people did not have an expectation of privacy in the numbers they dial since they know the numbers are used by the telco for a variety of business purposes, including call routing.

While the government contends that the third-party doctrine governs this case because cell-site records are business records created and maintained by the wireless carriers, the Court states that the government fails to account for the seismic shifts in digital technology that allows the tracking of not only Carpenter’s location for short periods but for years. In the Court’s view, the government does not ask for a straightforward application of the third party doctrine but instead seeks a significant extension to cover a distinct category of information. Recognizing that the third party doctrine stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another, the Court distinguishes this case from Smith and Miller based on the nature of the information. In Smith and Miller, the Court did not rely solely on the act of sharing but rather the limited nature of the particular documents sought (i.e., a pen register and bank records contain limited identifying information). Here, the Court suggests that there are no comparable limitations on the revealing nature of CSLI. Justice Robert states, “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 Court also rejects the rationale of voluntary exposure under the third-party doctrine. The Court asserts that CSLI is not truly shared because cell phones log a cell-site record automatically without any affirmative act of the user. “In light of the deeply revealing nature of CSLI,” Chief Justice Roberts writes, “its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection.” The Court concludes that given the unique nature of CSLI, that the government obtained the information from a third party does not overcome Carpenter’s claim to Fourth Amendment protection.

As the government did not obtain a warrant supported by probable cause before acquiring Carpenter’s cell-site records, but acquired the records pursuant to a court order requiring a showing of reasonable grounds, the showing falls short of the probable cause required for a warrant. As the Court usually requires “some quantum of individualized suspicion” before a search or seizure may take place, an order issued under the Stored Communications Act is not a permissible mechanism for accessing historical cell-site records. LE must obtain a warrant before compelling a wireless carrier to turn over a subscriber’s CSLI.15 Accordingly, the Court reversed and remanded the case for further proceedings consistent with its holding.


The Court did note that even though the government will generally need a warrant to access CSLI, case-specific exceptions may support a warrantless search of CSLI records such as exigent circumstances where LE needs are so compelling that a warrantless search is objectively reasonable under the Fourth Amendment. In addition, the Court cautions that its decision is a narrow one stating that it does express a view on matters not before it including real-time CSLI or “tower dumps” (a download of information on all the devices that connected to a particular cell site during a particular interval). The Court also clarifies that it does not disturb the application of Smith and Miller or call into question conventional surveillance tools, such as security cameras. Nor does the Court address other business records that might incidentally reveal location information. Further, the Court asserts that its opinion does not consider other collection techniques involving foreign affairs or national security.

The Court’s opinion is 119 pages, with the traditionally more liberal Justices (Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan) joining the majority opinion. Separate dissenting opinions were written by Justices Anthony Kennedy, Clarence Thomas, Samuel Alito and Neil Gorsuch. Justices Thomas and Gorsuch both argue that the Court has moved beyond what the framers intended the Fourth Amendment to protect. Justice Alito, while sharing some of the majority’s concerns, argues that the Court overreacted to new technology and will guarantee a blizzard of litigation while threatening many legitimate and valuable investigative practices upon which LE rely. And, Justice Kennedy argues that the Court has unhinged the Fourth Amendment from the longstanding property-based concepts and that the decision is inconsistent with earlier rulings finding people have no protections for records from third parties, from banks to cellphone companies.

1 Carpenter v. United States, ___ U.S. ___ No. 16–402 (June 22, 2018).
2 18 U. S. C. §2703(d).
3 Carpenter v. United States, 819 F. 3d 880 (2016).
4 Katz v. United States, 389 U. S. 347 (1967).
5 Smith v Maryland, 442 U.S. 735 (1979).
6 Boyd v. United States, 116 U. S. 616, 630 (1886).
7 United States v. Di Re, 332 U. S. 581, 595 (1948).
8 Kyllo v. United States, 533 U. S. 274 (2001).
9 Jones, 565 U. S. at 430
10 Riley v. California, 573 U. S. ___, ___ (2014) (slip op., at 27). No. 13–132
11 Jones, 565 U. S. at 415.
12 The Court notes that while the records in this case reflect the current state of technology, the accuracy of CSLI is approaching GPS-level precision, and the Court must take into account more sophisticated technology being developed.
13 United States v. Miller, 425 U. S. 435 (1976).
14 Smith v. Maryland, 442 U.S. 735 (1979).
15 The Court notes that the ultimate measure of the constitutionality of a governmental search is reasonableness, and warrantless searches are typically unreasonable where a search is undertaken by LE to discover evidence of criminal wrongdoing.

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