Summary of Supreme Court’s Decision in Carpenter v. United States

Published: Jun. 22, 2018

Updated: Oct. 05, 2020

In a 5-4 decision written by Chief Justice Roberts – and invoking the types of government oppression on liberty that led to the American Revolution —  the Supreme Court reversed the Court of Appeal’s decision and held that the government must obtain a warrant to search a target’s Cell-Site Location Information (“CSLI”). The Court found that customers have a reasonable expectation of privacy in CSLI based on the sweeping extent of location information collected, the automatic nature by which wireless carriers collect the information, the inferences that can be made about a person’s movements from such data, and the extent to which government could obtain information collected retroactively on hundreds of millions of phone users. According to the majority:

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 timestamped 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.” Jones, 565 U. S., 430, at 415 (opinion of SOTOMAYOR, J.). These location records “hold for many Americans the ‘privacies of life.’” Riley, 573 U. S. 400 (slip op., at 28) (quoting Boyd, 116 U. S., at 630).

Rejecting the government’s argument that there was no 4th Amendment protection in this data because it was previously disclosed to a third party, the Court refused to extend the third-party doctrine set down in Smith and Miller given the unique nature and persistence of cell phone location records.

Even more importantly, the Court strongly emphasized that the government must obtain a warrant, and cannot use a subpoena, to obtain 4th Amendment protected records in the hands of a third party, rejecting Justice Alito’s dissenting argument that the warrant requirement never applies when the government uses compulsory process, like a subpoena, to obtain information held by a business.

There are a few clear holdings from the case:

  • “An individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI.  The location information obtained from Carpenter’s wireless carriers was the product of a search.”  (Slip at 11).
  • The third party doctrine does not extend to CSLI because given “the unique nature of cell phone location information, the fact that the Government obtained the information from a third-party does not overcome Carpenter’s claim to Fourth Amendment protection. The Government’s acquisition of the cell-site records was a search within the meaning of the Fourth Amendment.”  (Slip at 17).
  • The third party doctrine still applies to bank records, telephone numbers, but its logic does not extend to a “detailed and comprehensive record of [a] person’s movements.” (Slip at 11).
  • Because the Government’s actions were a search, it “must generally obtain a warrant supported by probable cause before acquiring” CSLI. (Slip at 18).
  • The standard set forth in 2703(d) “falls well short of the probable cause required for a warrant.” (Slip at 19).
  • “This Court has never held that the Government may subpoena third parties for records in which the suspect has a reasonable expectation of privacy.” (Slip at 19).  “We hold only that a warrant is required in the rare case where the suspect has a legitimate privacy interest in records held by a third party.”  (Slip at 21).

Additionally, the Court made observations about CSLI that are equally applicable to other types of location information, such as GPS data. The Court noted that:

  • Even though CSLI is not as accurate as GPS information, this was not sufficient to avoid the need for a warrant. The Court noted that the data in Carpenter “placed him within a wedge-shaped sector ranging from one-eighth to four square miles” (Slip at 14).
  • The court noted that there is a “world of difference” between the types of personal information at issue in classic third party doctrine cases like Smith (dialed phone numbers) and Miller (bank transactional records) and the “exhaustive chronicle of location information casually collected by wireless carriers today.” And found that CSLI is far more revealing than telephone numbers.
  • The Court also seemed struck by the fact that CSLI is not truly “shared” – the majority noted that a cell phone logs location “by dint of its operation, without any affirmative act on the part of the users beyond powering up.” (Slip at 17).
  • CLSI is “an entirely different species of business record—something that implicates basic Fourth Amendment concerns about arbitrary government power much more directly than corporate tax or payroll ledgers. … If the choice to proceed by subpoena provided a categorical limitation on Fourth Amendment protection, no type of record would ever be protected by the warrant requirement.” (Slip at 20).

Notwithstanding the sweeping nature of the Court’s language, there are some things the court did not do. It did not rule on whether collection of location data in real-time, or for less than 7 days implicated the same Fourth Amendment concerns. It did not entirely jettison the Third Party Doctrine, nor did it apply its holding to other government collection techniques, such as “tower dumps,” or use of surveillance cameras in public places, or cases involving foreign affairs or national security. Instead, it invoked Justice Frankfurter’s warning from 1944 that the court should tread carefully in cases involving new innovations so as not to “embarrass the future.”