SCOTUS decides GPS monitoring is a search

Per Justice Scalia: "The Government’s attachment of the GPS device to the vehicle, and its use of that device to monitor the vehicle’s movements, constitutes a search under the Fourth Amendment."

Here's the opinion. This is a biggie, and a huge loss for the feds who were fighting hard. Scalia backs away from the traditional Katz test:

This conclusion is consistent with this Court’s Fourth Amendment jurisprudence, which until the latter half of the 20th centurywas tied to common-law trespass. Later cases, which have deviated from that exclusively property-based approach, have applied the analysis of Justice Harlan’s concurrence in Katz v. United States, 389 U. S. 347, which said that the Fourth Amendment protects a person’s “reasonable expectation of privacy,” id., at 360. Here, the Court need not address the Government’s contention that Jones had no “reasonable expectation of privacy,” because Jones’s Fourth Amendment rights do not rise or fall with the Katz formulation. At bottom, the Court must “assur[e] preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.” Kyllo v. United States, 533 U. S. 27, 34. Katz did not repudiate the understanding that the Fourth Amendment embodies a particularconcern for government trespass upon the areas it enumerates. The Katz reasonable-expectation-of-privacy test has been added to, butnot substituted for, the common-law trespassory test. See Alderman v. United States, 394 U. S. 165, 176; Soldal v. Cook County, 506 U. S. 56, 64. United States v. Knotts, 460 U. S. 276, and United States v. Karo, 468 U. S. 705—post-Katz cases rejecting Fourth Amendment challenges to “beepers,” electronic tracking devices representing another form of electronic monitoring—do not foreclose the conclusion that a search occurred here. New York v. Class, 475 U. S. 106, and Oliver v. United States, 466 U. S. 170, also do not support the Government’s position. Pp. 4–12.

Justice Sotomayor doesn't like this analysis and concurs to explain that all this old stuff may need to be re-examined in light of evolving technology:

More fundamentally, 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 greatdeal 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 cellu- lar 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 medi- cations they purchase to online retailers. Perhaps, asJUSTICE ALITO notes, some people may find the “tradeoff” of privacy for convenience “worthwhile,” or come to acceptthis “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 protectedstatus 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. See Smith, 442 U. S., at 749 (Marshall, J., dissenting) (“Privacy is not a discrete commodity, possessed absolutely or not at all. Those who disclose certain facts to a bank or phone company for a limited business purpose need not assume that this information will be released to other persons for other purposes”); see also Katz, 389 U. S., at 351–352 (“[W]hat [a person] seeks to preserve as private,even in an area accessible to the public, may be constitutionally protected”).

Justices Alito, Ginsburg, Breyer and Kagan also concur, but disagree with Scalia's property analysis, and would stick to the Katz reasonable expectation of privacy test.