On May 24, 1844, a crowd gathered inside the United States Supreme Court chambers in the basement of the Capitol, eagerly awaiting a demonstration of an amazing new communication technology. They watched as inventor Samuel F.B. Morse successfully sent the first long-distance telegraph message — “What hath God wrought?” — to a railroad station near Baltimore. While earlier demonstrations of the device had successfully sent messages between the House and Senate chambers, long-distance transmission was still an open question. Congress had provided $30,000 to underwrite Morse’s successful experiment.1 That day may well have marked the last time the Supreme Court was completely in step with modern communication technology.
Technological change inevitably presents new tools for the criminally minded. Law enforcement necessarily responds by using that same technology to develop new investigative tools to combat crime. In turn, the legislative and judicial branches adapt the law to the new technology to ensure that the proper balance is maintained between security and liberty.
Unfortunately, there is often a significant lag time between the arrival of new law enforcement technologies and the laws regulating their use. Moreover, the regulatory responses of the legislative and judicial branches are typically not well coordinated, significantly adding to the time delay before a fully formed regulatory scheme is in place.2
Carpenter v. United States3 is the latest installment of this cat-and-mouse regulatory game. For well over a quarter century, law enforcement has surreptitiously converted the personal cell phone into a tracking device, capable of compiling a comprehensive chronicle of the user’s movements over an extended period of time. Finally, the Supreme Court has confronted the constitutionality of this practice and determined that a warrant based on probable cause is required by the Fourth Amendment.4 In doing so, the Carpenter Court adopted a normative approach well suited for the question presented but long avoided by lower courts.5 It also significantly circumscribed the “third party doctrine”;6 this new limitation will no doubt reverberate throughout many decisions involving nonpublic databases that hold vast and ever-growing amounts of our digital data.7
Scholars debate whether the legislative or the judicial branch is better equipped to adjust the balance between security and privacy as new tools become available. In the case of cell phone tracking, both branches were slow and neither was effective, permitting millions of searches that have now been declared unconstitutional. One lesson of Carpenter is that courts must not be reluctant to confront the challenges of twenty-first-century technology. Another is that Congress and state legislatures need to design a better system for ensuring that law enforcement is subject to public accountability before using these powerful new surveillance tools.
* Interim Dean and Professor of Law, University of San Francisco School of Law. The author would like to thank Cera Armstrong for her extremely helpful research and editing help with this case comment.
** Director, Fourth Amendment & Open Courts, Center for Internet and Society, Stanford Law School. In July 2018, he retired as United States Magistrate Judge, Southern District of Texas, Houston Division.