William & Mary Law Review


In his 2001 majority opinion for Kyllo v. United States, Justice Scalia adopted his characteristic chiding tone to gently reproach what he saw as a notably liberal departure from the original textual interpretation of the Constitution. The Katz test for Fourth Amendment violations, to Scalia, was plainly “circular, and hence subjective and unpredictable.” That it was one of the most influential and oft-discussed decisions the Supreme Court has ever handed down made little difference; regardless of whatever Justice Harlan and his successors had said, the Fourth Amendment was, at its heart, a protection against government interference with property and had never been tied to “the quality or quantity of information obtained.”

Of course, Scalia’s property-centric reproach of Katz’s legacy was far from unprecedented. In fact, legal scholars as well respected as Judge Richard Posner of the Seventh Circuit Court of Appeals had been slinging the very same criticisms at the two-prong Katz test for years. No matter one’s opinion of either of these jurists, or of the ubiquitous “reasonable expectation of privacy” test, it would be difficult to argue that it has been easy to apply in practice. And the Court has, frustratingly, avoided directly addressing the issue. Given this, one might be tempted to join the textualists in their opinion that the old, easy-to-apply, property-based standard is superior.

That does not mean, however, that the Katz test has led to undesirable outcomes. In the age of modern technology, when the government has access to surveillance methods allowing unprecedented intrusion into the privacies of life, Americans are more conscious of their privacy interests than ever and less confident that those interests will be protected. For all the valid criticisms that may be levied against it, the Katz test, at the very least, offers an avenue for confronting these concerns.

This is exactly what happened when the Court rendered its decision in Carpenter v. United States, a landmark case extending Fourth Amendment protection to historical cell site location information (CSLI)—data generated, collected, and maintained by cell phone service providers entirely outside the control of the individuals the data describes. Reactions to Carpenter varied, but it should be clear to anyone who understands the history and context behind the Court’s decision that it represents a direct repudiation of the notion that the appropriate Fourth Amendment analysis is not “tied to measurement of the quality or quantity of information obtained.” In fact, the Carpenter analysis was explicitly tied to both the quantity and quality of the information at stake.

But the problem remains unaddressed, as the Court has yet to outline an all-encompassing approach to Fourth Amendment cases of unwarranted government surveillance that do not involve physical trespass. These kinds of cases rarely overrule each other, so it seems intuitive that the Court should be able to establish some consistent through line. Yet, so far, it has not. This Note proposes that it can be done, but only if the Court readily admits that the Fourth Amendment no longer protects only property, but also information. The ultimate outcome of Carpenter, and of every case that has adequately applied the Katz test, has been to keep certain information out of government hands.

Somewhat ironically, this includes Kyllo. It is from the language of Kyllo, originally intended to protect the traditionally privileged space of the home, that this Note draws inspiration for its proposed rule: absent probable cause, the Fourth Amendment proscribes the government from obtaining information that could not otherwise have been obtained without resorting to surveillance technology or physically trespassing on private property. This relatively simple standard, which can be called the obtainable information rule, unifies the collective holdings of post-Katz surveillance cases and provides a flexible framework for future decisions and new technologies.

In order to understand exactly how the obtainable information standard works, it is important to place it in the historical context of Fourth Amendment doctrine. Part I of this Note will examine the history of Fourth Amendment doctrine in cases of government surveillance since 1967 and leading up to Carpenter v. United States, a landmark case of critical importance to this argument. Part II will explore some of the theories proposed by academics for reconstructing, clarifying, or otherwise refining Fourth Amendment surveillance doctrine in a palatable manner, and will explain why each is unsatisfactory in at least one regard. It will then formally propose the obtainable information standard as a satisfactory alternative, capable of unifying post-Katz surveillance jurisprudence under a single theory. Part III will discuss the intersection between the obtainable information standard and third-party doctrine, which has become a subject of much discussion (and concern) following Carpenter. It will explain how the third-party doctrine need not be thrown out the window in order to accommodate the proposed standard.

Finally, it is worth noting that the purpose of this Note is not to argue that the obtainable information rule is the solution most resonant with the original meaning of the Fourth Amendment. Rather, the primary purpose of the rule is to synthesize the various holdings of the Supreme Court since Katz into a single, easy-toapply standard. As Part II will explain, there is also good reason to believe that it is the most functionally desirable rule, but this Note does not address the contention that any or all of the Supreme Court’s holdings since Katz were themselves unconstitutional and should be overruled.