The Supreme Court issued an important ruling on Thursday in a 4th Amendment case, saying that the police must get a warrant before obtaining data from cell phone companies that show someone’s location and travels based on their contact with cell transmission towers. The ruling was 5-4, with Chief Justice Roberts joining the four liberals on the court in the majority, a highly unusual lineup.
In this case, a man named Timothy Carpenter was arrested and eventually convicted for a series of armed robberies and the police tracked him through his cell-site location information (CSLI), but without getting a warrant. The state argued that he had no expectation of privacy because the cell phone company already had that data, but Roberts, writing for the court, forged a slightly different path from those precedents based on modern technology. The district and appeals court agreed with the state, but those rulings are now overturned. The brilliant Amy Howe explains the ruling:
In a decision joined by Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan, Roberts characterized the case as involving two, potentially conflicting lines of the Supreme Court’s precedent. The first involves whether someone like Carpenter can expect to have his whereabouts kept private. Roberts acknowledged that in some of its decisions predating the digital era, the court had ruled that a driver should not expect his movements on public roads to be kept private. But, Roberts stressed, times have changed. People would not expect police to track their every movement over long periods of time, but that is exactly what the cell-site location records here do. Indeed, Roberts suggested, because people carry their phones virtually everywhere with them, cell-site location records provide the government with “near perfect surveillance, as if it had attached an ankle monitor to the phone’s user” – not only going forward but also going back up to five years.The second line of precedent, Roberts continued, is the third-party doctrine. But this is not exactly, Roberts emphasized, a “garden-variety request for information from a third party” because of the “seismic shifts in digital technology that made possible the tracking of not only Carpenter’s location but also everyone else’s, not for a short period but for years and years.” When the Supreme Court decided the cases establishing the doctrine, he explained, it was dealing with relatively “limited types of personal information”; no one could have envisioned that cellphones would be so ubiquitous and provide so much information about their users for so long. And, he added, because cellphones are such a pervasive part of life “that carrying one is indispensable to participation in modern society,” it can’t really be said that a cellphone user is voluntarily sharing information about his location with his carrier – another rationale for the third-party doctrine. Because of the “unique nature” of cell-site location information, Roberts concluded, the third-party doctrine does not apply, and the acquisition of the cell-site location records was a search within the meaning of the Fourth Amendment, for which the government would generally have to obtain a warrant.
As usual, it’s a fairly narrow ruling from Roberts. He left open the possibility that someone could be tracked in real time by their cell location data in “exigent circumstances,” but that is the long-established and usual loophole in the 4th Amendment so it doesn’t change much. It’s good to see Roberts come down on the side of privacy and civil liberties here and discouraging that four justices saw it otherwise. You can read the full ruling here.