Back to the Future: Kyllo, Katz, and Common Law

Abstract

Commissioned in connection with a symposium at the University of Mississippi School of Law on the effect of technology on Fourth Amendment rights, this article assesses the significance of the Supreme Court's recent decision in Kyllo v. United States. The ruling in Kyllo was relatively narrow: police officers need a warrant to aim a thermal imaging device at a house. But the Court's reasoning was expansive. Led by Justice Scalia, the majority took the occasion to set ground rules for determining when any new technology of surveillance constitutes a search and thus must comply with the requirements of the Fourth Amendment. In doing so, the Court substantially reinterpreted Katz v. United States and rethought the relationship between the Fourth Amendment and common law, a relationship that over the past decade has come to figure prominently in the Court's approach to the Fourth Amendment. Kyllo can easily be seen as a repudiation of Katz and a continuation of the originalist turn in search-and-seizure law, but that reading is mistaken. In some respects Kyllo is strikingly faithful to Katz. It strongly reaffirms, for example, the Court's holding in Katz that a search requires no trespass or physical intrusion. And the originalism in Kyllo is not the originalism the Court has applied in other recent Fourth Amendment cases. The use of history in Kyllo is looser, and it has a different focus. The Court has shifted its attention, if only temporarily, from the content of eighteenth-century rules of search and seizure to what those rules accomplished. In these respects the methodology of Kyllo itself represents something of a return to the past - albeit to a past more open to the future. If the Court means what it says in Kyllo, the new Fourth Amendment originalism has been modified for the better. Kyllo may also point the way toward a better understanding of Katz, depending on how the Court answers two questions that Kyllo leaves open. The first concerns the measure of Fourth Amendment protection outside the home. Kyllo treats the home as a special place for Fourth Amendment purposes - hardly a novel proposition for the Supreme Court, but one that throws into doubt not only the reasoning of Katz, as it usually has been understood, but also the narrow holding of the case, that electronic surveillance of telephone conversations constitutes a search. The solution lies in recognizing that the Fourth Amendment protects communications as well as places - or, to use a modern metaphor, that virtual places as well as physical places can receive Fourth Amendment protection. The second question Kyllo leaves open is whether devices like thermal images are regulated by the Fourth Amendment only so long as they remain uncommon. The answer should be no, but that defending this answer may require the Court to reconsider certain other features of search-and-seizure law - features that are due for reconsideration in any event.