Kagan was unpersuaded by Dreeben’s attempt to distinguish dragnet surveillance by GPS devices from dragnet surveillance by cellphone tracking. “In both cases, you have reliance on a new technology that allows for 24/7 tracking,” she said. “Now, you’re exactly right, there were different means, but in both cases, you have a new technology that allows for 24/7 tracking and a conclusion by a number of justices in Jones that that was an altogether new and different thing that did intrude on people’s expectations of who would be watching them when.”

At this point, Justice Sonia Sotomayor jumped in. In Jones, Sotomayor wrote an important and prescient analysis of the challenge that confronts the Court as it attempts to translate the Fourth Amendment into a world where our most intimate data is stored not in locked desk drawers, but in the digital cloud. “I for one doubt that people would accept without complaint the warrantless disclosure to the Government of a list of every Web site they had visited in the last week, or month, or year,” she wrote. “I would not assume that all information voluntarily disclosed to some member of the public for a limited purpose is, for that reason alone, disentitled to Fourth Amendment protection.”

In the Carpenter argument, Sotomayor elaborated on her claim in the Jones case that Americans do not expect the government to reconstruct their movements in public and private by seizing electronic data without good reason. She asked Dreeben, “What do you do with the survey mentioned by your opposing colleague that says that most Americans, I still think, want to avoid Big Brother? They want to avoid the concept that government will be able to see and locate you anywhere you are at any point in time.” Sotomayor added, “Do you really believe that people expect that the government will be able to do that without probable cause and a warrant? The Constitution protects the rights of people to be secure. Isn’t it a fundamental concept, don’t you think, that that would include the government searching for information about your location every second of the day for months and months at a time?”



Throughout the argument, Sotomayor gave concrete and convincing examples of how pervasively Americans use their cellphones and how invasive warrantless cellphone tracking could become. “Why is it not okay, in the way we said about beepers, to plant a beeper in somebody’s bedroom, but it’s okay to get the cellphone records of someone who I—I don’t, but I know that most young people have the phones in the bed with them,” she asked to laughter. “All right? I know people who take phones into public restrooms. They take them with them everywhere. It’s an appendage now for some people. If it’s not okay to put a beeper into someone’s bedroom, why is it okay to use the signals that phone is using from that person’s bedroom, made accessible to law enforcement without probable cause?”