As previously reported, the Supreme Court on November 29 heard arguments in Carpenter v. United States, an important privacy case about the Fourth Amendment’s application to 127 days’ worth of a criminal suspect’s cell-site location information. While the Court has yet to decide the case, its decisions last week in Byrd v. United States and earlier this Term in District of Columbia v. Wesby (argued by one of this post’s authors) hint of trouble ahead for the government.

Byrd and Wesby: A practical rather than technical reading of the Fourth Amendment

While the facts were quite different in Byrd and Wesby, the decisions share a common theme. In both, the Supreme Court rejected analytical shortcuts that did not reflect the real world.

Byrd involved a police search of a rental car trunk yielding contraband, including forty-nine bricks of heroin. The lower courts accepted the government’s argument that the driver could not object to the search under the Fourth Amendment because “drivers who are not listed on rental agreements always lack an expectation of privacy in the automobile based on the rental company’s lack of authorization alone.” The Supreme Court decisively rejected this “per se rule.” It noted how there are “countless innocuous reasons why an unauthorized driver might get behind the wheel of a rental car and drive it” and how “car-rental agreements are filled with long lists of restrictions.” A breach of an agreement would not automatically mean the driver lacked even the reasonable expectation of privacy necessary to claim Fourth Amendment protection. (The same might be argued of email providers’ fine-print-laden Terms of Service, as the Electronic Frontier Foundation and Orin Kerr have noted.) But the Court also rejected the competing argument that the sole occupant of a rental car “always” has an expectation of privacy, and so it remanded for a ruling based on the precise facts rather than categorical rules.Wesby involved a very different situation, but a similarly practical Fourth Amendment ruling. The case involved whether police officers had probable cause to arrest apparent trespassers found at a raucous, late-night party in a near-vacant house they did not have permission to enter. There were a lot of facts, but the lower court keyed on just one: some partygoers claimed that an absent person had invited them into the house. The lower court then ruled that no other particular piece of evidence gave the police sufficient reason to disbelieve this claim of invitation and thus to think the partygoers knew or should have known they lacked permission to be in the house. The Supreme Court reversed, faulting the lower court for its “excessively technical dissection” of the evidence and its failure to consider “the whole picture.” Probable cause, the Court emphasized, cannot be “reduced to a neat set of legal rules.” Despite the claim of invitation, the totality of the circumstances allowed a reasonable inference that “the partygoers were knowingly taking advantage of a vacant house as a venue for their late-night party.”

Carpenter: Will the Court accept the government’s reliance on the third-party doctrine?

The approach taken in Byrd and Wesby should worry the government in Carpenter. This important privacy case asks whether a cell phone user under criminal investigation was searched within the meaning of the Fourth Amendment, and thus could invoke its protections, after the government obtained court orders requiring wireless service providers to turn over cell-site location information revealing his location and movements over the course of about four months. The government’s main response in its brief is based on the “third-party doctrine”: when a person voluntarily turns over information to third parties, the government’s acquisition of records containing such information from third parties that create them is not a “search” to which he can object.

But, much as in Byrd and Wesby, the Court may think the simplicity of that response masks the practical complexities that should matter. Indeed, at oral argument, the government was pressed on how well its argument maps onto the real world – for instance, Justice Kagan noted the privacy implications of the government’s argument as applied to “new technology that allows for 24/7 tracking” and Chief Justice Roberts questioned whether a cell phone user’s disclosure of location information really is voluntary in a practical sense.

The decision in Carpenter is expected by the end of June. Stay tuned.