The Carpenter Adjustment

With the Supreme Court set to hear oral argument on April 27th in United States v. Chatrie, the geofence warrant case, I’m pleased to be able to post The Carpenter Adjustment, which is Chapter 9 of my 2025 book, The Digital Fourth Amendment.  In the chapter, I explain what I think Carpenter means, the moves it is making, and how I think courts should interpret it.  You can read the chapter here.

Here’s the chapter summary:

The chapter considers how courts should interpret Carpenter v. United States (2018), the Supreme Court’s blockbuster ruling that cell-site location records are protected under the Fourth Amendment. Carpenter is the Supreme Court’s equilibrium-adjustment for noncontent network information: it recognizes that some network metadata is new and that the translation from physical space to network environments should treat some metadata differently. The question is, Which Internet data qualifies? This chapter develops a three-part test to apply Carpenter to Internet information. It then applies the test to a few important types of Internet information, such as Internet protocol addresses, geofence warrants, trip information, and Google search terms.

Ideally one would read this chapter in the context of the entire book, but I think this 20-page chapter stands on its own relatively well.