In November 2011, the University of San Diego Moot Court Board hosted the 23rd Annual Criminal Procedure National Tournament. This year’s problem was written by USD Moot Court Executive Board member Matthew Stephens. One of the two issues argued in the competition was whether warrantless installation and use of a GPS tracking device on a suspect's vehicle to monitor its movements on public streets violates the Fourth Amendment.
 
Earlier this week, the United States Supreme Court answered with a unanimous "yes" in United States v Jones, 565 U. S. __ (2012), but the justices differed widely on their reasoning.

The majority opinion, authored by Justice Scalia (joined by Chief Justice Roberts and Justices Kennedy, Thomas, and Sotomayor), presents the case as a fairly straightforward search and seizure case of the physical trespass variety. The Fourth Amendment guarantees persons the right "to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures…" Jones' vehicle is his "effect." Law enforcement  physically intruded upon Jones' vehicle in the process of installing and receiving data from the GPS tracking device.  In true Originalist fashion, Scalia reasons that the framers would have recognized such physical intrusion as a search and, therefore, it constitutes a search.

Scalia summarily dispenses with more recent cases that have addressed GPS and other surveillance technology under a "reasonable expectation of privacy" analysis introduced in under Katz v. United States, 389 U.S. 347 (1967). He reasons that this case requires no "reasonable expectation of privacy" analysis because the Fourth Amendment protects against, at a minimum, physical trespass. The "reasonable expectation of privacy analysis" is only required for actions that do not involve a physical trespass.  In Scalia's words, "the Katz reasonable-expectation-of-privacy test has been added to, not substituted for, the common-law trespassory test." Jones, slip op. 8.

In compartmentalizing physical trespass searches separately those involving no physical trespass, the court avoids answering the bigger questions about the Fourth Amendment (and other privacy law) implications of current and future technologies.

Justice Sotomayor joined Justice Scalia's opinion (winning him the majority) but also filed her own concurring opinion. Justice Sotomayor endorses Justice Scalia's framing of physical trespass searches: "the trespassory test applied in the majority’s opinion reflects an irreducible constitutional minimum: When the Government physically invades personal property to gather information, a search occurs." Jones, slip op. Sotomayor concurrence, 2. But Justice Sotomayor goes on to express concern over searches that do not involve physical trespass, even when the party seeking to protect a privacy interest has willingly provided the contested information to a third party.

Justice Alito's concurring opinion (joined by Justices Ginsburg, Breyer, and Kagan) rejects Justice Scalia's analysis of physical trespass searches, asserting that the "reasonable expectation of privacy" analysis set out in Katz provides the exclusive test for all Fourth Amendment cases. In particular, Justice Alito points to Oliver v. United States, 466 U. S. 170 (1984), in which a police trespass onto a suspect's "open field" was found not to constitute a search within the meaning of the Fourth Amendment: "[I]n determining whether expectations of privacy are legitimate. ‘The premise that property interests control the right of the Government to search and seize has been discredited’" (citations omitted). Jones, slip op., Alito concurrence, 6.

There's no shortage of commentary in the blawgosphere – here are just a few posts:

Washington Post: Robert Barnes, Supreme Court Warrants Needed in GPS Tracking

Slate: Dahlia Lithwick,  US v Jones Supreme Court Justices Alito and Scalia brawl over technology and privacy

SCOTUS Blog: Tom Goldstein, Reactions to Jones v. United States: The government fared much better than everyone realizes
 
SCOTUS Blog: Lyle Denniston, Opinion Recap Tight Limit on Police GPS Use

NY Times: Adam Liptak, Justices Say GPS Tracker Violated Privacy Rights

Volokh Conspiracy Blog: Orin Kerr, What Jones Does Not Hold

Concurring Opinions Blog: Derek Bambauer, Why Scalia is Right in Jones: Magic Places and One-Way Ratchets

Concurring Opinions Blog: Priscilla Smith, United States v. Jones: Privacy in Public Space? Piece it all Together and You Get 5

Concurring Opinions Blog: Paul Ohm, Jones is a Near-Optimal Result

Concurring Opinions Blog: Margot Kaminski, Three thoughts on U.S. v. Jones

[JML]