News You Can Use: Carpenter v. United States – the latest from SCOTUS on 4th Amendment Protections for Cellphone Data

Carpenter v. US

When you use a cell phone you leave a footprint of your location. To send and receive information, cell phones connect to the cell tower that is geographically closest. The connection leaves an approximate map of where you are and where you were. This information is collected and stored by private cell phone carriers and often sold to private parties for market research. In Carpenter, the Supreme Court held that police will generally need a warrant to obtain this cell-site location information (CSLI).


Timothy Carpenter was sentenced to nearly 116 years’ imprisonment for several armed robberies of Radio Shack and T-Mobile stores. The government’s case hinged on the cell phone records which placed Mr. Carpenter in the vicinity of the robberies at the time of the crimes. The government obtained these records after receiving an order from a magistrate judge compelling disclosure. In order to receive the order from the magistrate judge, the government had to provide “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.” 18 U.S.C. § 2703(d). This standard falls far short of the probable-cause standard demanded for the issuance of a warrant.

Before trial, Mr. Carpenter move to suppress the CSLI records arguing that they were obtained without a warrant. The district court denied the motion and the Sixth Circuit Court of Appeals affirmed.


Writing for the majority, Justice Robert observed that the issue fell in the middle of two seemingly incompatible lines of caselaw. The first line involves the “reasonable expectation of privacy” standard. The Court has held that “when an individual seeks to preserve something as private,” and his expectation of privacy is “one that society is prepared to recognize as reasonable . . . that official intrusion into that private sphere generally qualifies as a search and requires a warrant supported by probable cause.”

The second line of cases concerns what has been deemed the “third-party doctrine.” “A person has no legitimate expectation of privacy in information if he voluntarily turns it over to third parties.” In Carpenter, the question was whether such private data gleamed from cells phone could be subject to Fourth Amendment protections despite it being collected by a third-party. The Court held that it could.

The Court premised its holding on the fact that cell-site record are “qualitatively different” from the type of records historically subject to the third-party doctrine. CSLI offers “a detailed and comprehensive record of the person’s movement” and “hold[s] for many Americans the ‘privacies of life.’” CLSI provides “a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years.” Thus, “the fact that the information it is held by a third party does not by itself overcomes the user’s claim to Fourth Amendment protection.”

Thus any access of the record “invaded Carpenter’s reasonable expectation of privacy in the whole of his physical movements.” In other words, there can still be a Fourth amendment violation even if the information was handed over to a third party. “Whether the Government employs its own surveillance technology . . . or leverages the technology of a wireless carrier. . . an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI.”

The Court also downplayed the notion that the information was voluntarily provided to the third-party. “Cell phone location information is not truly ‘shared’ as one normally understands the term. In the first place, cell phones and the services they provide are such a pervasive and insistent part of daily life that carrying one is indispensable to participation in modern society. Second, a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the part of the user beyond powering up.” Accordingly, “in no meaningful sense does the user voluntarily assume the risk of turning over a comprehensive dossier of his physical movements.”


Justice Thomas dissented because he believes the Court should do away with the reasonable- expectation-of-privacy test.

Justice Alito dissented on the grounds that the Fourth Amendment does not apply to documents such as bank records or, in this case, cell phone data.

Finally, and most interestingly, Justice Gorsuch dissented because he would do away with both the third-party doctrine and the reasonable-expectation-of-privacy test and instead adhere to a test that determined whether someone had a “property interest” in the record. But Gorsuch noted that such an argument was not made in Carpenter and could not be decided on the record as it existed.


Carpenter is a narrow decision.  It expressly leaves open whether police would need a warrant to obtain “real-time CSLI” (same-time tracking) or “tower dumps” (a download of information on all the devices that connected to a particular cell site during a particular interval).”


  • Carpenter overrules United States v. Thompson, 866 F.3d 1149 (10th Cir. 2017) (holding that the third-party doctrine prevented a finding that the cell phone records were protected by the Fourth Amendment).
  • Carpenter chips away at the third-party doctrine in that it makes clear that “[o]ne does not surrender all Fourth Amendment protection by venturing into the public sphere.”
  • Always object to the introduction of CSLI obtained without a warrant