What’s the Status of the Mosaic Theory After Jones?

In its opinion below in what became United States v. Jones, the D.C. Circuit introduced a new “mosaic” theory of the Fourth Amendment. Under that theory, whether government conduct is a search is measured not by whether an individual act is a search, but rather whether the collective sum of the different acts over time amount to a search. Although that argument didn’t get much play in the Supreme Court briefs or at argument, it surfaced this morning in the Jones opinions. And perhaps the most fascinating aspect of the Jones opinions is that there appears to be a majority ready to embrace the mosaic theory, at least in some form.

Let’s start with Justice Alito’s concurring opinion for himself, Ginsburg, Breyer, and Kagan. Alito’s concurring opinion is mostly devoted to criticizing Scalia’s new trespass theory. But near the end of his concurrence, Alito then turns to how he would decide Jones:

[R]elatively short-term monitoring of a person’s movements on public streets accords with expectations of privacy that our society has recognized as reasonable. See Knotts, 460 U. S., at 281–282. But the use of longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy. For such offenses, society’s expectation has been that law enforcement agents and others would not—and indeed, in the main, simply could not—secretly monitor and catalogue every single movement of an individual’s car for a very long period. In this case, for four weeks, law enforcement agents tracked every movement that respondent made in the vehicle he was driving. We need not identify with precision the point at which the tracking of this vehicle became a search, for the line was surely crossed before the 4-week mark. Other cases may present more difficult questions. But where uncertainty exists with respect to whether a certain period of GPS surveillance is long enough to constitute a Fourth Amendment search, the police may always seek a warrant. We also need not consider whether prolonged GPS monitoring in the context of investigations involving extraordinary offenses would similarly intrude on a constitutionally protected sphere of privacy. In such cases, long-term tracking might have been mounted using previously available techniques

It sounds like Alito is using what I have elsewhere called the “probabilistic” approach to the reasonable expectation of privacy test, where an expectation of privacy is reasonable based on what a reasonable person would expect, and then he is allowing for at least some sort of mosaic aggregation. Thus, echoing the D.C. Circuit, Alito appears to be looking at whether the government conduct taken over time collects an amount of information that is somehow surprising or unexpected.

In his majority opinion, Justice Scalia concludes that the mosaic theory need not be addressed, but that it is a “novelty” that raises “thorny problems” if embraced. Responding to Alito, Scalia writes:

There is no precedent for the proposition that whether a search has occurred depends on the nature of the crime being investigated. And even accepting that novelty, it remains unexplained why a 4-week investigation is “surely” too long and why a drug-trafficking conspiracy involving substantial amounts of cash and narcotics is not an “extraordinary offens[e]” which may permit longer observation. See post, at 13–14. What of a 2-day monitoring of a suspected purveyor of stolen electronics? Or of a 6-month monitoring of a suspected terrorist? We may have to grapple with these “vexing problems” in some future case where a classic trespassory search is not involved and resort must be had to Katz analysis; but there is no reason for rushing forward to resolve them here.

That brings us to Justice Sotomayor, whose concurring opinion was sort of with Scalia, sort of with Alito, and then hints at being even more pro-privacy than either one. Sotomayor calls the Scalia rationale for the case “an irreducible constitutional minimum,” but she then goes on to look favorably on Alito’s opinion:

As JUSTICE ALITO incisively observes, the same technological advances that have made possible nontrespassory surveillance techniques will also affect the Katz test by shaping the evolution of societal privacy expectations. Post, at 10–11. Under that rubric, I agree with JUSTICE ALITO that, at the very least, “longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy.” Post, at 13. . . .

Sotomayor then goes on to discuss the nature of GPS surveillance specifically, and then writes:

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.

Fascinating. What’s particularly interesting to me is that the mosaic theory seems like a revolutionary new approach to Fourth Amendment law, and yet here 5 Justices seem ready to embrace it without even really recognizing how dramatic the change might be or what it might mean. Perhaps that means that the Justices see it as having some non-obvious limitation that makes it narrower than it might seem. Perhaps it only would apply to GPS devices or beepers, for example? Or perhaps the Justices just didn’t think too deeply about the issue and the complications it raises — perhaps because Scalia came forward with his new trespass test and any other theory would just be dicta?

Either way, the biggest surprise of Jones is that the mosaic theory lives. And it may have five votes. As always, stay tuned.