Note: The Supreme Court ultimately ruled in 2018 as hoped in this 2017 post, that a warrant is required to secure cell-tower data.

Civil libertarians, criminal defendants and their lawyers, and (some) Fourth Amendment scholars alike have long yearned for the eventual death of the so-called “third-party doctrine.” Or, at least, they have longed for its eventual dismemberment. That time may well be nigh. The court is considering a certioari petition (Carpenter v. United States, No. 16-402) that squarely raises the issue whether cellphone users have a reasonable expectation of privacy in “cell site location information” (records of where a cellphone user has been based on where she was at the time she made a call), even though they share that information with their respective cellphone service providers.

The third-party doctrine asserts that a person forfeits a reasonable expectation of privacy in a given piece of information the moment she discloses that information to a third party. Once she has done so, the police may obtain that information from the third party without a warrant because such an act is not a “search” within the meaning of the Fourth Amendment. The rule is derived from two cases from the 1970s in which the Supreme Court determined that Fourth Amendment “searches” did not occur when the used a “pen register” to capture the telephone numbers that a suspect had dialed and when the police obtained a suspects bank records from a bank. Smith v. Maryland, 442 U.S. 735 (1979); United States v. Miller, 425 U.S. 435 (1976). In both cases, the Court reasoned, the suspect had voluntarily surrendered the information at issue to a third party, thereby forfeiting any expectation of privacy in the information that society would be prepared to deem “reasonable.”

The third-party doctrine had a brief brush with disaster in United States v. Jones, 132 S. Ct. 945 (2012). In that case, the Supreme Court had to determine whether it constituted a “search” for Fourth Amendment purposes when the police attached a GPS monitor to a suspect’s car. A majority of the court concluded that it did, because such an act would have given rise to a cause of action for trespass in the 18th century. (Naturally, the late Justice Scalia, a champion of property rights in the Fourth Amendment context, authored the lead opinion.) A plurality of the Court, however, recognized that advances in GPS and communication technology have created a law-enforcement environment permitting near-ubiquitous surveillance under the third-party doctrine regime. See id. at 428-29 (Alito J., concurring in the judgment); 417-18 (Sotomayor, J., concurring) (“[I]t may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties.”).

Should the Court grant certiorari and conclude that there is a reasonable expectation of privacy in cellphone-tower data, it will likely do so on the basis that technology has so far advanced from the “pen registers” and the like of the 1970s that the third-party doctrine, as applied to such information, no longer stands up to scrutiny. It may even conclude, as the Fifth Circuit has, that each cellphone-tower data case should be treated on a case-by-case basis: that a warrant should be required only when the reviewing magistrate concludes that the the location information sought will show sensitive information (such as, for example, being in a constitutionally protected place).

The truth, however, is that the third-party doctrine was never sensible to begin with, and the court would be wise to dispose of it altogether. The technological sophistication of the information at issue should never have been the point: rather, the overarching point (observed ad nausem by commentators) is that it defies common sense to suppose that a person completely relinquishes a reasonable expectation of privacy whenever she communicates something to a third party. For example, the Court has argued that, because a person voluntarily provides records to a bank, that voluntariness establishes a willingness to reveal the information, thereby extinguishing the expectation of privacy that would otherwise protect it.  Miller, 425 U.S. at 442. The key error is that the Court’s rationale presupposes that the person does not expect that the bank will keep the information private. Barring some strong indications to the contrary, it seems far more likely that disclosures to a bank (or to most other people one shares private information with) are intended to remain “between the speaker and the hearer,” and therefore reasonably expected to be private.

Whatever comes of the Carpenter petition, the longevity of the third-party doctrine will eventually come under the watchful eye of the Supreme Court. With any luck, the Justices will curtail it or, even better, dispose of it altogether. The court should, rather than look to whether the suspect has voluntarily disclosed the information, determine whether that disclosure is of the kind that society would recognize as private (that is, that society would assume would not be publicized). In other words, the Court should apply the law as it existed before it fell of the wagon with the third-party doctrine in the first place.