Because I teach criminal procedure but write mostly about the First Amendment (I do have some Fourth Amendment pieces), I read Fourth Amendment cases differently from First Amendment cases. The Supreme Court’s decision in Carpenter v. United States is exciting because it holds that government use of cell site data to determine a defendant’s location over a period of seven days is a search, requiring probable cause and a warrant. Perhaps even more exciting, Carpenter promises to be a joy to teach.
There are so many reasons why Carpenter will be a great teaching case. Skeptical (and anxious) students prefer precise answers to thorny legal questions, but also need to be pushed to recognize a case’s inherent ambiguities and open questions. The majority and dissenting opinions give the reader snippets of clarity but also plenty of work to do to find coherence with underlying principles for future application. The case also straddles the line between “third-party doctrine” cases, so it recruits line-drawing and analogical reasoning skills. Plus, fundamentals of the doctrine are challenged by several Justices. The different opinions grapple with the relationship between property and privacy, and the Court also wades into confused areas like the connection between the Fourth Amendment and the subpoena power. This case has everything, even a lesson in cell phone technology!
Some of the most pedagogically interesting aspects of Carpenter: