Introduction
The Digital Fourth Amendment is written by Professor Orin Kerr, one of the country’s foremost authorities on the Fourth Amendment, electronic privacy, and criminal procedure.1 Kerr’s work has been deeply influential in shaping how courts are looking at and deciding issues raised by law enforcement’s powerful and novel capabilities, thanks to technological changes.2 He has written “more than 80 law review articles, more than half of which have been cited in judicial opinions, including eight articles referenced in U.S. Supreme Court decisions.”3
While Kerr started his career at the Department of Justice, it would be inaccurate to say that he brings a strictly pro–law enforcement attitude to the conversation. Kerr knows that technology has generally been a boon for law enforcement and has put the public’s privacy rights at a disadvantage (p. 39). The primary purpose of his book is to argue that courts should interpret the Fourth Amendment to account for this shift in the balance of power (p. 42). In several of his recommendations, Kerr would adopt stronger constitutional protections, even when this position would disadvantage law enforcement compared to the current status quo.4 He has provided model briefs for defendants seeking to suppress social-media evidence that the government forced providers to copy and preserve without first getting a warrant.5 And he has sometimes sided with defendants in criminal cases.6 His work is cautious and conservative (p. 43),7 and courts respect that, regardless of which side of the “v” Kerr’s name appears on.
While Kerr got his start in law enforcement, I spent my first nine years out of law school as a criminal defense lawyer in San Francisco. Most mornings I was at the City’s Hall of Justice, an “austere” building from the outside,8 yet inside teeming with people confronting the worst moments of their lives, and the lawyers who are supposed to help them. I got to see the Fourth Amendment at work, and I was not impressed. A police officer justified a warrantless search, testifying “he said I could look in his pockets,” as the man sitting at the defendant’s table vigorously shook his head “no.” Officers conducted a warrantless search of a car with a drug-sniffing dog,9 and found several kilos of cocaine, after the driver was stopped for “excessive honking” at a vehicle blocking the entryway to a housing complex he was visiting. That vehicle? The police put it there.
At the time, the internet was relatively new, and I left criminal defense work to help develop Stanford Law School’s Center for Internet and Society, thinking “this new technology gives society a chance to start afresh and do a better job.”
Today, I am an ACLU lawyer with the national office’s Speech, Privacy, and Technology Project.10 As you might imagine, the cutting-edge privacy issues we work on substantially overlap with Kerr’s Fourth Amendment scholarship. When Kerr agrees with our positions, we are always delighted to have him as an ally before the court.
More often though, we disagree, collegially.11 As experts, he and I are often both invited to conferences to speak on novel privacy-and-technology issues. I have debated Orin so many times on so many panels at so many conferences,12 and then had a glass of wine with him afterward; I consider him an out-of-the-court friend.
The Digital Fourth Amendment takes on a topic that judges struggle with every day. Law enforcement has embraced powerful surveillance technologies that enable investigations that could never have taken place as little as twenty years ago (p. 2). Courts must decide whether and how to allow the government to use these powerful tools (pp. 3–4). Searches and seizures of data from computers, cell phones, and online accounts also raise complicated questions about the appropriate role of the Fourth Amendment in protecting the vast amount of data that we generate in our daily lives.
Kerr tackles these questions with characteristic clarity and persuasiveness. His writing is lively and can successfully be understood by lay people. Make no mistake, though: It is valuable and important for experts, too. Search warrants for electronic information are commonplace.13 Only law enforcement is in the room, these processes are often sealed, and most of them stay secret forever.14 The absence of published judicial decisions means conversations among scholars and advocates — such as those presented in Kerr’s book (and in book reviews like this one) — are critical to public understanding and democratic decision-making regarding difficult privacy questions.
In Part I of this Review, I describe the observations Kerr makes in his book, focusing on his original theory of “equilibrium-adjustment” (original both in the sense that Kerr identified and named it, and in that it is connected with the interpretive theory of constitutional originalism). Kerr argues that equilibrium adjustment is the proper framework in which to consider the Fourth Amendment in connection with novel surveillance techniques in our digital and online world, and I generally agree with him. In Part II, I review some criticisms of equilibrium adjustment as a theory. In Part III, I describe and criticize15 Kerr’s application of equilibrium adjustment to some specific challenges, including searches of electronic devices and metadata, geofence searches, mosaic theory, and border searches. Overall, The Digital Fourth Amendment should cement Kerr’s reputation as one of the country’s most scholarly authorities in this field. Also, sometimes he gets things wrong.