This past Monday, Fourth Amendment watchers began gathering at the Supreme Court on the eve of oral argument in United States v. Jones. Narrowly, the case was to resolve a circuit split on whether law enforcement can surreptitiously place a GPS device on a car, and then monitor movements for an extended period of time. More broadly, Jones presents the Court with a vexing question: Does modern technology necessitate a stronger Fourth Amendment? Justice Alito succinctly summarized the issue when he noted that Fourth Amendment protection has historically relied on the logistical impossibility of institutionalized surveillance, a reliance that has become misplaced as new technologies emerge.

Early in oral arguments, the Court grappled with whether or not Jones could be decided on the narrow ground that police had committed a trespass. In fact, the Court returned to that question later, asking counsel for Respondent Antoine Jones whether 1) affixing a GPS device to a license plate, rather than the undercarriage of the car, would effect a trespass; and 2) whether affixing an inert device would effect a Fourth Amendment violation. Justice Alito pressed his peers to consider the broader question. He noted that this particular trespass would have nominal effect if not for the character of its consequences. That is, if not for the information gathering process it enabled.

To advance the government’s argument, Deputy Solicitor General Michael Dreeben relied heavily on United States v. Knotts. Dreeben argued that the warrantless use of GPS was squarely within a range of practices already recognized as constitutional. In Knotts, the Court announced that: “A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.” On Tuesday, however, the Court appeared uneasy with the government’s reliance on Knotts and suggested many grounds for distinguishing the case. The police in Knotts, for example, had surveilled their suspect on a single journey. Further, the beeper that police attached to the suspect’s car still required them to remain within a delimited proximity of the suspect’s vehicle. Visual contact was unnecessary, but police could not—as Chief Justice Roberts noted—merely sit in headquarters. The government responded to the Chief’s assertion that GPS technology is “dramatically different” from the beepers used in Knotts by resting on outcomes. GPS “doesn’t expose anything . . . that isn’t already exposed to public view for anyone who want[s] to watch.”

Factual distinctions aside, Justice Scalia provided theoretical grounds for departing from Knotts.  After expressing frustration with precedent established by United States v. Katz, which injected privacy into the Fourth Amendment by holding that a Fourth Amendment violation occurs whenever a reasonable expectation of privacy is violated, Justice Scalia said,

It is one thing to add that privacy concept to the Fourth Amendment as it originally existed and it is quite something else to use that concept to narrow the Fourth Amendment from what it originally meant.

Despite his reluctance to recognize the government’s doctrinal argument, Justice Scalia did question whether this issue was one for the legislatures. Given the line-drawing problems that surfaced when the Court tried to establish the difference between monitoring a single journey, and monitoring of a more systematic character, the political approach could have some traction. Justice Scalia captured the line-drawing problem well by analogizing to a simple mathematical axiom. If monitoring for one day presents no constitutional problem, then monitoring for thirty presents no constitutional problem, because 100 x 0 = 0. That assessment differs markedly from one that Chief Justice Roberts drew out of the Respondent’s brief, that one day’s monitoring is a tile, but a month’s is a mosaic. Of course Justice Scalia’s political approach may have other benefits. Technological change occurs rapidly, and trusting legislators to regulate would likely allow for more flexible oversight.

Administrability concerns aside, the Court expressed real concern with the “1984 scenario.”  Justice Breyer asserted that systematic, institutionalized surveillance might be unreasonable, even if there was no individual violation of a right to privacy. He said,

If you win this case then there is nothing to prevent the police or the government from monitoring 24 hours a day the public movement of every citizen of the United States. . . . And no one, at least very rarely, sends human beings to follow people 24 hours a day. That occasionally happens. But with the machines, you can.

Justice Sotomayor added that the government seemed to be advocating dragnet surveillance, surveillance similar to the type that the Framers hoped to prohibit by forbidding general warrants.

Ultimately, genuine uncertainty pervaded the Court. Justices seemed hesitant to resolve the case on narrow grounds, but skeptical that a principled line could be drawn. Because the case implicates other forms of surveillance—like closed circuit television, which is used in Britain—it has attracted lots of attention. The Jones case will likely turn on whether institutionalized surveillance is unreasonable, whether it violates a threshold expectation of privacy. If it does, the Justices may adopt the government’s alternative argument: that police need reasonable suspicion to monitor without consent. The Justices may also simply require a warrant.

More here and here, oral arguments available here.