Supreme Court Justice Sonia Sotomayor filed an interesting and heartening concurring opinion in U.S. v. Jones, yesterday's decision concluding that tracking a suspect's car by attaching a GPS device to it amounts to a "search" under the Fourth Amendment. Although Sotomayor joined the majority opinion by Antonin Scalia, she clearly was concerned about the limits of his rationale, which focused on the trespass involved in attaching the transmitter and therefore did not address surveillance technologies that do not require physical contact with the target's property (citations omitted):
Physical intrusion is now unnecessary to many forms of surveillance. With increasing regularity, the Government will be capable of duplicating the monitoring undertaken in this case by enlisting factory- or owner-installed vehicle tracking devices or GPS-enabled smartphones. In cases of electronic or other novel modes of surveillance that do not depend upon a physical invasion on property, the majority opinion's trespassory test may provide little guidance.
In such cases, Sotomayor says, the "reasonable expectation of privacy" test used in Samuel Alito's concurring opinion (which was joined by three other justices) would apply, and she suggests that extended tracking of people's movements, regardless of the specific means used, would constitute a "search" under the Fourth Amendment (citations omitted):
GPS monitoring generates a precise, comprehensive record of a person's public movements that reflects a wealth of detail about her familial, political, professional, religious, and sexual associations. The Government can store such records and efficiently mine them for information years into the future. And because GPS monitoring is cheap in comparison to conventional surveillance techniques and, by design, proceeds surreptitiously, it evades the ordinary checks that constrain abusive law enforcement practices: "limited police resources and community hostility."
Awareness that the Government may be watching chills associational and expressive freedoms. And the Government's unrestrained power to assemble data that reveal private aspects of identity is susceptible to abuse. The net result is that GPS monitoring–by making available at a relatively low cost such a substantial quantum of intimate information about any person whom the Government, in its unfettered discretion, chooses to track–may "alter the relationship between citizen and government in a way that is inimical to democratic society."
I would take these attributes of GPS monitoring into account when considering the existence of a reasonable societal expectation of privacy in the sum of one's public movements. I would ask whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on. I do not regard as dispositive the fact that the Government might obtain the fruits of GPS monitoring through lawful conventional surveillance techniques. I would also consider the appropriateness of entrusting to the Executive, in the absence of any oversight from a coordinate branch, a tool so amenable to misuse, especially in light of the Fourth Amendment's goal to curb arbitrary exercises of police power to and prevent "a too permeating police surveillance."
Judging from this discussion, there is already a fifth vote on the Court for the position that warrantless GPS tracking violates the Fourth Amendment even when it does not involve physical intrusion. But Sotomayor goes even further, questioning "the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties," which has been the Court's position since the 1970s. Sotomayor suggests "this approach is ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks," such as the phone numbers and email addresses with which the communicate, the websites they visit, and the online purchases they make:
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. But whatever the societal expectations, they can attain constitutionally protected status only if our Fourth Amendment jurisprudence ceases to treat secrecy as a prerequisite for privacy. 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.
Sotomayor is right to question that assumption. It seems to me this kind of information, although held by third parties, is the modern equivalent of the "papers" specifically protected by the Fourth Amendment.
Look for more on U.S. v. Jones in my column tomorrow.