To make matters even more confusing, as Tom Goldstein pointed out at SCOTUSBlog, most of the mainstream media misinterpreted the opinion to say a warrant is required to use GPS tracking on a personal vehicle. But the ruling does not address the warrant requirement, only whether the GPS tracking constituted a "search."
What's the distinction? The Fourth Amendment only bans "unreasonable" searches without a warrant, but the courts have carved out wide swaths of legal territory where warrantless searches are routinely allowed. Wrote Goldstein, "The government probably conducts fifty times as many warrantless searches a day as warrant-based searches. The government can sometimes conduct warrantless searches on less than probable cause, as when a police officer pats down someone on the street or TSA puts carry-on luggage through an x-ray machine." I'd also add consent searches at traffic stops and searches incident to arrest as examples of warrantless searches. They're far more common than search warrants, and there's no guarantee this ruling will require a warrant in every instance GPS is used by federal agents, particularly when it's used for a relatively brief period of time.
In an earlier post, Goldstein discussed the breakdown among justices as insightfully as I've seen on this case:
I think that the correct way to understand the case is to read it as having two separate majority opinions. This odd alignment occurs because Justice Sotomayor agrees with both theories: she agrees with the majority “at a minimum” (Sotomayor op. at 1) and also seemingly agrees with the concurrence’s “incisive” conclusions (id. at 3). Justice Sotomayor does not formally join the Alito opinion, but her sympathy for its finding of a Fourth Amendment “search” in GPS monitoring is fairly obvious, as she expresses a broader view of privacy than any other member of the Court.Votes on Fourth Amendment questions tend to defy partisan makeup. In Jones, basically court conservatives and Sotomayor sided with Scalia for the majority opinion expanding the Fourth Amendment's scope, while Alito teamed up with those considered the "liberal" wing to denounce the expansion and critique Scalia's judicial activism.
Here is the upshot. Five Justices join the holding of the “majority” opinion (per Scalia) that by attaching and monitoring a GPS device the police conduct a “search”; four Justices (those in the Alito concurrence) reject that view. Five Justices join or express their agreement with the portion of the “Alito” opinion concluding that the long-term monitoring of a GPS device violates a reasonable expectation of privacy; four Justices (those in the majority, minus Sotomayor) leave that question open.
Seldom do 9-0 rulings reveal such sharp, underlying disagreement. But that's not the biggest story coming out of the case, which surely marks one of the most important moments in Fourth Amendment jurisprudence in the last 50 years. As Orin Kerr pointed out at the Volokh Conspiracy, Scalia's majority opinion articulated a new test for what constitutes a search, reaching back to historic court precedents based on property rights as opposed to modern jurisprudence based on a "reasonable expectation of privacy," first articulated in the Katz decision in 1967. That case, which dealt with an eavesdropping device planted in a phone booth (ask your parents or watch an episode of Dr. Who if you don't know what that is), found that “the Fourth Amendment protects people, not places” abandoning the "trespass" model.
Scalia's opinion, though, demands that a defendant's "Fourth Amendment rights do not rise or fall with the Katz formulation" and makes the claim that "Katz did not narrow the Fourth Amendment’s scope." That's a matter of opinion and I surely disagree with it. I think Katz significantly narrowed the Fourth Amendment's scope by placing the focus almost solely on "reasonableness," and that this opinion reinforcing other aspects - in particular, the enumerated, protected places and items - represents a welcome corrective, broadening the Fourth Amendment's scope instead of narrowing it for the first time in decades.
Regardless, according to Scalia's most recent pronouncement, "the Katz reasonable-expectation-of-privacy test has been added to, not substituted for, the common-law trespassory test." So going forward, the court has effectively added a new definition of what is a search while keeping the old one intact, expanding the scope of the Fourth Amendment in some as-yet-to-be-defined way.
Though I happen to agree with Scalia's policy choice in this case, it's pretty clear he's the one adding to Fourth Amendment jurisprudence, expanding the definition of a search beyond its Katz-based limits. Justice Alito called the majority opinion "unwise," declaring that "It strains the language of the Fourth Amendment; it has little if any support in current Fourth Amendment case law; and it is highly artificial." For Alito, as the court had expressly declared in its Kyollo ruling, the Katz opinion “decoupled violation of a person’s Fourth Amendment rights from trespassory violation of his property,” which is certainly how this non-lawyer always understood it. While IMO Alito's concurrence accurately reflects the trajectory of Fourth Amendment stare decisis, Scalia's back-to-basics approach revitalizes aspects of the Fourth Amendment that the Katz approach brushed past too breezily in the name of reasonableness.
Justice Sonia Sotomayor received a great deal of attention for her concurrence, in which she expressed the fear 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'm glad somebody said it!)
Even "more fundamentally," wrote Sotomayor, "it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties." Hear, hear! That indeed is the great dark cloud looming over Americans' privacy frontier. Too bad the court's second-most junior justice couldn't get any of her colleagues to sign onto the sentiment that the court should address the question.
Just to mention it, for us here in Texas this ruling only applies to federal agents, as we already have a requirement that law-enforcement get a court order before placing a "mobile tracking device" on your car.
MORE: From Lori Andrews at The Crime Report. Here's a related editorial from the Houston Chronicle.