In a decision that defines how the Fourth Amendment applies to information collected in the digital age, the Supreme Court today held that police must use a warrant to obtain from a cell phone company records that detail the location and movements of a cell phone user.  The opinion in Carpenter v. United States limits the application of the third-party doctrine, holding that a warrant is required when an individual “has a legitimate privacy interest in records held by a third party.”

The 5-4 decision, written by Chief Justice John Roberts, emphasizes the sensitivity of cell phone location information, which the Court described as “deeply revealing” because of its “depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection.”  Given its nature, “the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection,” the Court held.

As we previously reported, Carpenter stems from a criminal investigation in Detroit in 2011, where the government acted without a warrant in obtaining 127 days’ worth of cell phone location records for two suspects.  The government obtained the data under the Stored Communications Act, 18 U.S.C. §§ 2703(c)(1)(B), (d), which requires a showing of reasonable suspicion — but does not require probable cause.  For one suspect, the records revealed 12,898 points of location data; for another, 23,034 location points.  Both suspects were convicted, based in part on cell phone location evidence that placed them near the crime scenes.

Sensitivity of Information

In requiring a warrant to obtain cell phone location information, the Court emphasized the sensitivity of that information, which it called “an entirely different species of business record” than bank records or phone numbers.  Cell phone location information “implicates basic Fourth Amendment concerns about arbitrary government power much more directly than corporate tax or payroll ledgers,” the Court explained.  Throughout the majority decision, Chief Justice Roberts invoked his 2014 opinion in Riley v. California to underscore the sensitivity of this information.  As Riley recognized, a cell phone today is almost a “feature of human anatomy” that “tracks nearly exactly the movements of its owner.”

The Court also focused on the “near perfect surveillance” achieved by cell phone location records — and lack of resource constraints in obtaining them.  Before the digital age, law enforcement officers could surveil a suspect for brief periods of time but doing so “for any extended period of time was difficult and costly and therefore rarely undertaken.”  Unlike traditional surveillance methods, “cell phone tracking is remarkably easy, cheap, and efficient,” the Court said.  “With just the click of a button, the Government can access each carrier’s deep repository of historical location information at practically no expense.”  Cell phone location records thus provide information “otherwise unknowable,” as if the Government “had attached an ankle monitor to the phone’s user.”  Moreover, the Court emphasized, cell phone location information is collected on all cell phone users — not just individuals under investigation — meaning the “newfound tracking capacity runs against everyone.”

Limits of Third-Party Doctrine

In concluding the third-party doctrine did not apply to cell phone location information, the Court said the information “does not fit neatly under existing precedents.”  Rather, it falls at the “at the intersection of two lines of cases.”  The first line addresses an individual’s expectation of privacy in his physical locations and movements.  The second line embodies the third-party doctrine, under which an individual has no legitimate expectation of privacy in information voluntarily turned over to third parties.

While Carpenter does not overrule the third-party doctrine, it substantially limits its application.  Applying the third-party doctrine to cell phone location information would not be a “straightforward application” as the Government urged, but a “significant extension” of the doctrine that the Court rejected.  The Government’s invocation of the third-party doctrine “fails to contend with the seismic shifts in digital technology,” the Court found.

According to the Court, there is “a world of difference between the limited types of personal information addressed in” the third-party doctrine cases and “the exhaustive chronicle of location information casually collected by wireless carriers today.”  Moreover, the information is “not truly ‘shared’ as one normally understands the term.”  In part, that is because “[v]irtually any activity on the phone” generates location information.  “Apart from disconnecting the phone from the network, there is no way to avoid leaving behind a trail of location data.”  As a result, the Court held that users do not voluntarily assume the risk of turning over a comprehensive dossier of their physical movements, the Court held.  It emphasized that the case is not about a person’s momentary location while “using a phone” but “about a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years.”

Ramifications of Decision

Chief Justice Roberts emphasized that the opinion of the Court was narrow, noting that it does not overrule the third-party doctrine or affect cases relating to foreign affairs or national security.  According to the majority, the decision also does not call into question “conventional surveillance techniques and tools” nor apply to “other business records that might incidentally reveal location information.”  Justice Kennedy disagreed with this characterization of the Court’s opinion, observing in dissent that the decision “will have dramatic consequences for law enforcement, courts, and society as a whole.”  According to Justice Kennedy, the majority’s reasoning will “extend beyond cell-site records to other kinds of information held by third parties.”

Justices Alito, Thomas, and Gorsuch also filed separate dissents.  Justice Gorsuch’s dissent advocated for a property-based approach to the Fourth Amendment that would abandon both the third-party doctrine and the reasonable expectation of privacy test.  That approach would focus on whether the individual has a property interest in the records at issue.  Under that framework it is “entirely possible a person’s cell site data could qualify as his papers or effects,” Justice Gorsuch observed, even though a cell phone carrier holds the information.  But Carpenter failed to raise a property-based argument before the district court, the court of appeals, or the Supreme Court, and therefore “forfeited perhaps his most promising line of argument,” according to Justice Gorsuch.

Like Justice Kennedy, Justices Alito and Thomas argued in separate dissents that cell phone location information belongs to cell phone companies, not to cell phone users, and thus did not qualify for protection under the Fourth Amendment.  Justice Thomas focused on the fact that Carpenter “did not create the records, he does not maintain them, he cannot control them, and he cannot destroy them.”  Justice Alito also cautioned that the majority’s decision was overly broad and would invite a “blizzard of litigation” because the majority opinion offered “no meaningful limiting principle, and none is apparent.”