Implementing Carpenter

I recently posted a new draft article, “Implementing Carpenter,” on the Supreme Court's blockbuster June 2018 decision in Carpenter v. United States. The article consists of two draft chapters of a forthcoming book, “The Digital Fourth Amendment,” which will be published by Oxford University Press. I'd love your critical feedback. I found these chapters tough to write and the line-drawing exercises Carpenter requires very challenging. But I did my best to make them and justify them, and I'd rather you throw rotten fruit at me now instead of when the book comes out. So if you have feedback, please send it on.

The document I posted has two chapters. The first chapter, “The Carpenter Shift,” explains how Carpenter takes the Fourth Amendment in a new direction and explains the new state of the law. After explaining the conceptual basis of Carpenter and why it's a considerable departure from prior law, the chapter tries to reduce Carpenter to a doctrinal test. Based on a close read of the opinion and the broader theory of equilibrium-adjustment driving it, the chapter argues that Carpenter applies to non-content Internet records otherwise left unprotected when three conditions are met. First, the records must be new kinds of records of the digital age. Second, the records must not have been generated by meaningful voluntary choice beyond what is necessary to participate in modern life. Third, the records must be of a type that can reveal an intimate window into a person's life.

The second chapter, “Implementing Carpenter,” applies those general principles. It first focuses on the challenging question of how to identify a Carpenter search in a particular case. How do you measure a privacy invasion? Does a search occur when an intimate fact was actually revealed in an investigation? Does it occur when the government gets enough records that the revealing of an intimate fact would be expected, the so-called Mosaic Theory? After going through the pros and cons of different approaches, the chapter concludes that the best way to measure an invasion of privacy is a source rule: Any government collection of any amount of Carpenter-protected information, no matter how small or unilluminating in a particular case, should be treated as a search.

Finally, the chapter applies Carpenter to several important cases. It identifies two kinds of Internet non-content metadata that should trigger Carpenter: to/from information about messaging services, such as e-mail and text messages, and monitoring the websites a person visits. When the government wants to conduct surveillance of who a person e-mailed or messaged, or it wants to install a monitoring device to see what websites a person is visiting, collecting that metadata should be a Fourth Amendment search. It also identifies a few examples of metadata collection that should not trigger a search: acquisition of voice call metadata, the IP addresses a person was assigned while connected to the Internet and records of ride-sharing services such as Uber of Lyft. The chapter concludes by arguing that downstream analysis such as data mining should not itself trigger a search, although the prospect of downstream analysis can change whether a particular record is protected under Carprenter and can trigger the Fourth Amendment upstream for all compelled acquisition of that kind of record.

Comments very welcome. Thanks as always for reading.

(Cross-posted at The Volokh Conspiracy)