SCOTUS Builds New Fourth Amendment Protections for Cell Location Data with Carpenter

Person recording concert on phone
The Supreme Court of the United States recently tackled privacy in the mobile age and agreed that cell phone location is something that is protected.

The primary question that is asked in these cases is what is a reasonable expectation of privacy? In Fourth Amendment jurisprudence, the answer is two-fold, referring to both a subjective expectation (an individual’s belief that a certain place or thing is private) and an objective expectation (society’s willingness to recognize certain places or things as private). Where the two overlap, the expectation of privacy is reasonable and, therefore, protected by the Constitution. This means that an attempt by the government to invade this privacy requires a warrant. In Carpenter v. United States, 585 US ___ (2018), the Supreme Court decided, in a narrow 5-4 ruling, that, within certain limits, cell phone location records fall within this area.


As background, Carpenter was one of four men arrested in connection with a series of armed robberies. One of the suspects provided the FBI with his cell phone number along with the numbers of the three other men, one of whom was Carpenter. Using this information, the FBI was able to obtain transactional records for each number which included the date and time of calls, and cell site location information, i.e., the approximate location where calls began and ended based on their connection to cell towers. The government obtained this information in reliance upon the Stored Communications Act, under which access to cell site location information (CSLI) requires only “reasonable grounds” for believing the data is “relevant and material to an ongoing investigation.” Using these records, the government charged Carpenter with aiding and abetting robbery.

Carpenter moved to suppress the CSLI evidence, arguing that the warrantless search and seizure of cell phone records, which provides the location of cell phone users, violates the Fourth Amendment. The government relied upon past Supreme Court cases in arguing that an individual has no privacy right in information he voluntarily turns over to a third party, such as a wireless carrier, and therefore Fourth Amendment protections should not apply.The Court disagreed.

The Court’s Opinion

The Supreme Court decided that government acquisition of CSLI is a search under the Fourth Amendment, and, thus, generally requires a warrant. Chief Justice Roberts, joined by Justices Ginsburg, Breyer, Sotomayor and Kagan, explained that CSLI paints a detailed picture of a person’s physical location compiled “every day, every moment, over several years.” The comprehensiveness of this picture involves privacy concerns greater than those the court considered in earlier cases because intimate details can be learned about individuals from the places they visit—sexual preferences from a visit to a gay bar, political associations from their presence at a rally, religious beliefs from a stop at a mosque, and so on. “In light of the deeply revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection,” Roberts wrote, “the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection.” Given this, the court declined to accept the government’s argument that CSLI is similar to the business records at issue in other Fourth Amendment cases in which it was decided that the sharing of information with a third-party negated the expectation of privacy.

The decision in Carpenter is narrow. It does not disturb previous decisions applying the third party doctrine, nor does it address other business records that might incidentally reveal location information. It makes clear that the government must obtain a warrant, supported by probable cause, when seeking more than six days of CSLI records (a shorter time span does not require a warrant). Only time will tell whether this interpretation remains limited or is expanded beyond Carpenter.

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