I recently posted a new draft of my latest article, An Equilibrium-Adjustment Theory of the Fourth Amendment, which recently was accepted for publication in the Harvard Law Review. In this post, I wanted to summarize the argument for readers who don’t feel like wading through 60 pages of law review writing.
Here’s the basic idea. Fourth Amendment law regulates criminal investigations. Specifically, it regulates when and how the police can collect evidence to prove crimes beyond a reasonable doubt. Fourth Amendment law faces a recurring problem, though: The facts of crimes and the facts of investigations are constantly changing. The bad guys are constantly coming up with new ways to avoid being caught, and the cops are constantly coming up with new ways to catch them. As a result, Fourth Amendment law is constantly facing new facts to regulate. In some cases the new facts reflect new technologies, used by the police, criminals, or both. And in other cases the new facts reflect new crimes or new social practices.
My argument is that there turns out to be a surprisingly common and surprisingly simple way that courts respond to this problem — and that response ends up explaining a remarkable amount of Fourth Amendment law. Courts respond to the new facts by trying to restore the old level of protection. If a new technology or practice increased government power, courts ratchet up Fourth Amendment protection to lessen government power. If a new technology or practice decreased government power, courts loosen protection to restore government power. The result is a correction mechanism. It’s kind of like the experience of driving over mountainous terrain: You add gas on the uphill and let off the pedal on the downslope, all in an effort to maintain constant speed. That’s what judges do when they come across new facts in Fourth Amendment cases.
My claim is that this very simple dynamic ends up explaining a great deal of search and seizure law. Today’s Fourth Amendment law is a product of hundreds of these adjustments — adjustments to restore the prior equilibrium points — generated over many years. If you open a book on the Fourth Amendment and just start learning the rules, the rules seem almost random, as every fact pattern seems to have its own special treatment. But if you take a historical approach and see how each new fact pattern emerged and threatened the status quo, you can begin see the rules in each area as reflecting localized efforts to restore the status quo in light of what was then a new technology or practice. It turns out to be a remarkably common instinct among judges, and one shared by pragmatists, originalists, textualists, living constitutionalists, and pretty much every other kind of “-ist” out there.
Anyway, that’s the basic idea. The article has the details, as well as a discussion of the normative implications of the theory and conditions on its use, so check it out if you’re interested.