Carpenter v. United States


 Can law enforcement acquire historical cell site location data without a warrant?  

Oral argument: 
November 29, 2017

In 2011, Petitioner Timothy Carpenter was arrested on suspicion of participating in a string of armed robberies in and around Detroit. In the course of the investigation, FBI agents acquired transactional records from Carpenter’s cell phone carrier. The government sought this data pursuant to the Stored Communications Act, which allows law enforcement to obtain communications records by demonstrating “specific and articulable facts” that the records are relevant to an ongoing investigation, rather than probable cause that a crime has been committed. The trial court denied Carpenter’s motion to suppress the records, and a jury convicted him of firearms violations and violations of the Hobbs Act. On appeal, Carpenter maintained that the acquisition of his cellular data without a warrant violated his Fourth Amendment rights, but the Sixth Circuit held that such a seizure did not constitute a “search” under the Fourth Amendment. Carpenter now challenges this classification of cell site data, arguing that the seizure of such data does constitute a search, and that the data is distinct from phone and bank records, which have not been afforded Fourth Amendment protection. This case could have significant consequences for the government’s ability to collect data that reveals a cell phone user’s location.  

Questions as Framed for the Court by the Parties 

Whether the warrantless seizure and search of historical cell phone records revealing the location and movements of a cell phone user over the course of 127 days is permitted by the Fourth Amendment. 


In April 2011, police arrested four men suspected of committing multiple armed robberies at Radio Shack and T-Mobile stores in Detroit and its surrounding suburbs. United States v. Carpenter, 819 F.3d 880, 884 (Sixth Circuit 2016). One of the men confessed to FBI agents, telling them that over a four-month period the group had robbed nine stores in Michigan and Ohio. See id. In May and June of 2011, the FBI requested that magistrate judges issue warrants for various cell site records, asserting “‘that these records would provide evidence that Timothy Sanders, Timothy Carpenter and other known and unknown individuals’ had violated the Hobbs Act, 18 U.S.C. § 1951.” See id. The magistrates issued the warrants pursuant to the Stored Communications Act, which requires the government to demonstrate “specific and articulable facts showing that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing investigation.” See id; 18 U.S.C. § 2703(d) .

Petitioner Timothy Carpenter was charged with six violations of a federal robbery statute, in addition to a felony firearms violation. 18 U.S.C. §§ 924(c), 1951(a); Carpenter, 819 F.3d at 884. Before the trial began, Carpenter moved to suppress the cell site evidence, contending that, under the Fourth Amendment, the government can only seize records such as the cell site data after it obtains a warrant supported by probable cause. See id. The district court denied the motion. See id. At trial, an FBI agent provided expert testimony about the cell site data obtained from MetroPCS, Carpenter’s wireless carrier. See id. at 885. Relying on the logs of Carpenter’s phone calls, as well as the phone’s signals to various cell towers, the agent created maps showing that Carpenter’s phone was between a half-mile and two miles of each of the robberies’ locations. See id. A jury convicted Carpenter on all of the Hobbs Act counts, and all but one of the § 924(c) firearm counts. See id. The district court sentenced Carpenter to 1,395 months’ imprisonment. See id.

On appeal, Carpenter challenged the district court’s denial of his motion to exclude the cell site data from evidence. Carpenter, 819 F.3d at 886. The cell site data were classified as business records, and in Carpenter’s case, the data reflected a 127-day range that encompassed the robberies for which he was charged. See id. Carpenter argued that the Stored Communications Act provided an insufficient basis for the government to collect these records, and that the Fourth Amendment required the government to establish probable cause and obtain a search warrant before collecting his cell site data. Id. The Sixth Circuit disagreed. See id. at 887. Using the Supreme Court’s decision in Smith v. Maryland as its primary support, the court held that Carpenter’s cell data were business records that revealed nothing about the content of any phone calls, and were therefore not protected by the Fourth Amendment. See id. Distinguishing Carpenter’s records from the information at issue in United States v. Jones in which the Supreme Court established that “longer term GPS monitoring” could infringe on privacy, the Sixth Circuit emphasized the fact that Carpenter’s records were obtained from a third party, which in turn should have diminished his expectations that the records were protected. Carpenter, 819 F. 3d at 889. The court also pointed out that in passing the Stored Communications Act, Congress had already answered the question which Carpenter’s appeal raised—namely, whether the government’s collection of business records containing cell site data was a search for the purposes of the Fourth Amendment. See id. In keeping with this Congressional decision, the Sixth Circuit held that it was not. See id. at 890.

In September 2016, Carpenter petitioned the Supreme Court, which agreed to consider whether the Fourth Amendment permits the government to collect cell phone records revealing an individual’s location and movements over an extended period of time without first obtaining a warrant.



Carpenter argues that the government’s acquisition of his historical cell site location data constitutes a search under the Fourth Amendment because it violated the reasonable expectation of privacy that he had in that information. Brief for Petitioner, Timothy Ivory Carpenter at 14–15. Carpenter asserts that it is reasonable to expect that law enforcement will not be able to catalogue an individual’s every movement, and that the Court supported this position when it ruled that long term GPS monitoring of a suspect’s car was a Fourth Amendment search in United States v. Jones. See id. at 16. Carpenter points out that most American adults keep their phones on or near their person at all times. See id. at 17. Thus, Carpenter notes that collection of historical cell site location data can reveal where a person goes and who they associate with. See id.  at 17–18. Carpenter argues that this kind of record is more revealing than the information law enforcement would ordinarily be able to obtain through the use of traditional investigatory tools. See id. at 19. According to Carpenter, the accuracy of cell site location data means that it is not notably different from the GPS data that the Court found unacceptable in Jones. See id. at 24. Carpenter asserts that, like GPS tracking, cell site location data can expose an individual’s movements within a particular wedge-shaped sector. See id. at 24–26. Further, Carpenter notes that these sectors are becoming ever narrower as cell service providers deploy “micro” cells to cover smaller geographical areas. See id. at 27. Finally, Carpenter maintains that state and federal law support his claim that there is a reasonable expectation of privacy attached to cell site location data. See id. at 21. Here, Carpenter points to states that require a warrant before law enforcement can collect cell site location data, as well as 47 U.S.C. 222(c)(1) which states that cell service providers may not disclose location information without customer approval. See id. at 22.

Carpenter argues that the third party doctrine—indicating that information disclosed to third parties cannot be reasonably expected to be private—should not apply in this case because he did not voluntarily disclose his cell site location information and because this data is more sensitive than the records involved in either United States v. Miller (holding that a bank customer had no reasonable expectation of privacy in his checks, deposit slips, and financial statements) and Smith v. Maryland (holding that the plaintiff had no reasonable expectation of privacy over telephone numbers dialed from his home phone, which law enforcement collected using a pen register). Brief for Petitioner, at 35. Carpenter characterizes the third party doctrine as a single factor of the larger reasonable expectation of privacy analysis. See id. at 38. From this perspective, Carpenter asserts that the Court should focus on the comprehensiveness of cell site location data which, when aggregated over 127 days, exposes much more personal information than the telephone numbers in Smith or the financial documents in Miller. See id. Carpenter contends that under Jones it does not matter whether cell site location data reveals the content of personal communications—the GPS tracking in that case had nothing to do with content and the Court nevertheless held that it qualified as a search. See id. In addition, Carpenter claims that owning and using a cell phone is not a “voluntary” decision in any meaningful sense, because these devices have become “indispensable for full participation in family, social, professional, civic and political life.” Id. at 39–40.  In this vein, Carpenter alleges that the United States’ theory of the third party doctrine would place all electronic communications accomplished through service providers, including emails, outside the scope of Fourth Amendment protection. See id. at 45–46.

The United States responds that its collection of cell site location data is not a search under the Fourth Amendment because Carpenter could not have had a reasonable expectation of privacy over information that he voluntarily disclosed to a third party. Brief for Respondent, The United States of America at 15. The United States relies on Miller and Smith to support this assertion. See id. at 15–16. Like the plaintiffs in Miller and Smith, the United States asserts that Carpenter had no reasonable expectation of privacy over data that his provider compiled for its own business purposes based on standard commercial transactions. See id. at 18. The United States claims that cell phone users must have a general sense that their phones cannot function without connection to cell towers and that this connection necessarily conveys their location information to service providers. See id. at 19–21. Moreover, the United States notes that providers routinely explain this feature in their contractual terms of service. See id. at 19. In the federal law context, the United States points out that 47 U.S.C. § 222 allows providers to disclose location information “as required by law” and argues that this exception applies when law enforcement collects cell site location data pursuant to a court order issued under § 2703 of the Stored Communications Act (“SCA”). Id. at 21. The United States likewise challenges Carpenter’s invocation of state law, citing to precedent establishing these rules do not dictate the reach of the Fourth Amendment. See id. at 23. Finally, the United States disputes Carpenter’s claims regarding the accuracy of cell site location data. See id. at 24. In this case, the United States observes that the cell site location data placed Carpenter within a sector that contained approximately 1,000 buildings—this information alone did not allow law enforcement to place Carpenter at the scene of the crime. See id. at 28.

The United States further argues that application of the third party doctrine does not depend on the level of sensitivity of the information disclosed. Brief for Respondent, at 28. Indeed, the United States notes that in Miller the Court explained that there is no reasonable expectation of privacy for information turned over to third parties “even if it is revealed on the assumption that it will be used only for a limited purpose and the confidence placed in the third party will not be betrayed.” Id. at 29. In addition, the United States maintains that a focus on sensitivity will create line-drawing problems for law enforcement, who cannot view the contents of records before they request them. See id. at 30. The United States also asserts that an individual’s decision to expose his location to cell towers by using his phone is fully volitional. See id. at 32. In this regard, the United States points out that, like the average cell phone owner, the plaintiffs in Smith and Miller had little choice but to use the services of their phone company and bank. See id. at 31. Finally, the United States disputes Carpenter’s claim that the third party doctrine would vitiate a reasonable expectation of privacy in all electronic messages. See id. at 36. According to the United States, emails would still be protected because they contain the content of personal communications whereas cell site location data consists only of the routing information “necessary to get those communications from point A to point B.” Id. at 37. 


Carpenter argues that even if the court does not accept that he had a reasonable expectation of privacy in his cell site location data, that information is still protected under a property-based theory of the Fourth Amendment. Brief for Petitioner, at 32. Carpenter explains that a Fourth Amendment search occurs whenever the government seizes a person’s “papers” or “effects” without consent. See id. To establish that cell site location data is the equivalent of a “paper” or “effect,” Carpenter points out that 47 U.S.C. 222(c)(1)-(2) designates location information as “customary proprietary network information.” See id. at 33. Based on this provision, Carpenter asserts that Congress intended to protect against nonconsensual distribution of cell site location data and create a property interest in the information on behalf of consumers. See id. at 34. In other words, Carpenter contends that cell site location data belongs to the cell phone owner and not to his service provider. See id. Thus, Carpenter argues that the United States’ collection of this data was a form of trespass that the Fourth Amendment prohibits. See id. at 32. 

The United States asserts that Carpenter has no property interest in his cell site location data because he did not create and does not control these records. Brief for Respondent, at 41. The United States observes that 47 U.S.C. § 222 enumerates a number of exceptions authorizing disclosure of cell site location data without the customer’s consent. See id. at 41–42.


Carpenter argues that the United States’ acquisition of his cell site location data was unreasonable because the government failed to obtain a warrant. Brief for Petitioner, at 48. Carpenter challenges the claim that the Court should defer to the SCA, noting that Congress was not aware that cell site location data even existed when it enacted the statute in 1986. See id. at 50. According to Carpenter, this absence of knowledge suggests that the SCA gives no meaningful guidance on whether the warrantless collection of cell site location data is reasonable. See id. Carpenter also distinguishes the Court’s subpoena cases, pointing out that they do not address materials in which the holder had a reasonable expectation of privacy. See id. at 52. Finally, Carpenter contends that law enforcement’s interest in obtaining cell site location data is no greater than their interest in obtaining any other form of evidence that routinely requires a warrant and that the probable cause requirement is not unduly burdensome. See id. at 54–55. For Carpenter, this case boils down to three words: “get a warrant.” Id. at 58.   

The United States contends that its acquisition of Carpenter’s cell site location data was reasonable because law enforcement obtained a court order pursuant to the SCA. Brief for Respondent, at 44. This statute requires the government to demonstrate “specific and articulable facts showing that there are reasonable grounds to believe the records are relevant and material to an ongoing criminal investigation.” Id. at 46. The United States argues that this standard is appropriate under the Court’s precedents recognizing that administrative subpoenas used to obtain third party records do not require a probable cause warrant. See id. at 45–46. In addition, the United States maintains that the “specific and articulable” facts standard is entitled to deference because it represents Congress’ reasoned judgment as to how much compulsory process is required based on the competing interests of individual privacy and effective law enforcement. See id. at 53. The United States observes that cell site location data is particularly valuable for law enforcement in the early stages of an investigation before probable cause exists, helping them to “deflect suspicion from the innocent, aid in the search for truth, and judiciously allocate scarce investigative resources.” Id. at 51. Ultimately, the United States argues that even if collecting and storing cell site location encroaches on individual privacy, this conduct is attributable to corporate service providers who are not subject to the Fourth Amendment. See id.




According to Carpenter, the Sixth Circuit’s holding that the government’s warrantless acquisition of cell site location data is not a “search and seizure” under the Fourth Amendment significantly implicates ordinary citizens’ privacy rights. See Brief for Petitioner, Timothy Carpenter at 14. Carpenter contends that the holding’s implication is not that the government may obtain cell site location data from particular individuals who are the targets of particular investigations, but rather that the government can access records of any American’s location history over any period of time, without subjecting itself to judicial oversight. See id.

According to the Center for Democracy and Technology (“CDT”), writing in support of Carpenter, the fact that a third party such as a cell-service provider holds an individual’s sensitive personal information does not preclude that individual from asserting a reasonable expectation of privacy, particularly considering that Americans store an increasing amount of private data on their phones. See Brief of Amicus Curiae Center for Democracy and Technology, in Support of Petitioner at 16. The CDT argues that regardless of a third-party interest in one’s data, the sensitive nature of the information contained on phones, along with the fact that its collection by law enforcement in the analog era would have required a large surveillance operation, means that Fourth Amendment protections should apply. See id. at 25–27. The CDT points out that 127 days’ worth of location data amounts to records of Carpenter’s movements over that same period. See id. at 25. Finally, the CDT contends that the voluntary provision of cell site location data to a cell-phone provider does not mitigate the need for Fourth Amendment protections, since cell users cannot meaningfully be said to voluntarily provide their data in the first place. See id. at 21.

In contrast to Carpenter and the CDT’s claim that cell site location data is Fourth Amendment-protected information, Professor Orin Kerr, writing in support of the United States, argues that historical cell site data is more like eyewitness testimony from someone who observed suspicious conduct. See Brief of Professor Orin S. Kerr (“Kerr”), in Support of Respondent at 3. Kerr contends that the Fourth Amendment makes a crucial distinction between public and private activity, and that it only extends its protections to the latter. See id. at 3–4. Unlike the specific content of an email or a text message, historical cell site records, according to Kerr, are the digital version of public communication, which a law enforcement officer would be able to monitor without first obtaining a warrant. See id. at 6. Similarly, the National District Attorneys Association (“NDAA”), writing in support of the United States, claims that because a customer typically has no reasonable expectation of privacy in business’ records of their services, Carpenter cannot maintain a privacy expectation in MetroPCS’s cell site records of his phone. See Brief of Amicus Curiae National District Attorneys Association, in Support of Respondent at 7.  Alabama and a number of other states (“the States”), writing on behalf of the United States, add that most phone providers’ service contracts or privacy policies warn customers that the companies collect location data, and that they may disclose that data to law enforcement. See Brief for the States of Alabama et al., in Support of Respondent at 9. The States claim that MetroPCS’s disclaimer of this sort undermines Carpenter’s reasonable expectation of privacy regarding his cell site records. See id. at 10.

With regard to the nature of the data, the United States contends that the cell site data merely provides circumstantial indications of a user’s location. Brief for Respondent, the United States in Opposition at 21. Similarly, the United States claims, cell site records are incapable of reading any information relating to an individual’s family, religion, finances, or political affiliation that may be stored on a user’s phone, so Carpenter’s claim that the government’s acquisition of the records may reveal sensitive personal information is without merit. Id. at 21, 25.

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