Just a little Supreme Court footnote here. Back in January of 2012, the Court decided United States v. Jones, an interesting Fourth Amendment case that posed the question whether attaching a GPS device to a car without the owner’s knowledge constituted a “search” within the meaning of the Fourth Amendment. The Court unanimously concluded that it did, but they split 5-4 as to why. Five Justices (Scalia, joined by Roberts, Kennedy, Thomas, and Sotomayor) decided the case based on the “original understanding” that a physical intrusion on property was enough to trigger the Fourth Amendment; four (Alito, joined by Ginsburg, Breyer, and Kagan) would have preferred to decide the case on the more modern “reasonable expectation of privacy” test.
Fascinating to the Fourth Amendment crowd, though perhaps not of great interest beyond that. But check out Justice Sotomayor, who wrote a separate opinion in addition to joining Scalia:
it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties. E.g., Smith, 442 U. S., at 742; United States v. Miller, 425 U. S. 435, 443 (1976). 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. People disclose the phone numbers that they dial or text to their cellular providers; the URLs that they visit and the e-mail addresses with which they correspond to their Internet service providers; and the books, groceries, and medications they purchase to online retailers. Perhaps, as Justice Alito notes, some people may find the “tradeoff ” of privacy for convenience “worthwhile,” or come to accept this “diminution of privacy” as “inevitable,” post, at 10, and perhaps not. 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.
Remember, this is from well over a year before there was any public disclosure of the NSA program, and there is no reason to think that Justice Sotomayor was privy to what was going on at the FISA Court (indeed, if she were, she almost certainly would not have written her opinion the same way). Rather, her opinion shows a truly remarkable degree of prescience, along with a clear call for constitutional doctrine to keep up with technological changes that may render obsolete the Court’s previously-expressed ways of analyzing when people have a “reasonable expectation of privacy” and when they don’t. Good stuff.