At its heart, mathematics is a formal system with strict rules of proof. Pure mathematics is characterized in part by the search for exception and error, so much so that identifying a single flaw in an argument usually invalidates its associated claim unless and until the error is fixed. Once one moves beyond the realm of formal proof, however, mathematics becomes a rhetorical art.

Similarly, in the legal arena, even when the facts of a case are not in dispute, the interpretation and application of statutes and standards of evidence are open to argument, judgment, and appeal.

Lawyers and magicians, especially magicians who specialize in a branch of stage magic called mentalism, often use math in their arguments and presentations. Selecting the order of witnesses and exhibits, establishing the likelihood of an event by emphasizing the relative improbability of alternatives, and vastly overclaiming the importance of evidence and objections during summation all play a central role in trial strategy and tactics.

Rhetorical Mathematics in Magic and Law addresses these and other issues by showing how performers and advocates can:

• Manipulate both math (as practiced in the courtroom) and the law to move from persuasion to syllogism
• Use fact patterns to frame arguments and define ground at the start of proceedings
• Advance or challenge arguments based on conditional probability
• Construct novel presentations and methods designed to persuade audiences in the court and the theater

​Drawing on works such as Lawrence Tribe’s classic article “Trial by Mathematics: Precision and Ritual in the Legal Process”, Leila Schneps and Coralie Colmez’s popular book Math on Trial, and Ashley Saunders Lipson’s reference work Courtroom Use and Misuse of Mathematics, Physics, and Finance: Cases, Lessons and Materials, Rhetorical Mathematics interrogates the persuasive milieu where audiences encounter argument as finders of fact, participants in a magical demonstration, or both.

Kerr, Orin. The Digital Fourth Amendment: Privacy and Policing in Our Online World. Oxford University Press. 2025.
 
The Fourth Amendment to the United States Constitution limits how the government may conduct searches and seizures, with the effect that evidence can be excluded from trial if it was obtained in violation of that amendment. Technological advances such as the automobile, phone booth, and Internet have required courts to reinterpret Fourth Amendment law to accommodate these novelties.
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Lower courts often differ in their interpretations and, after the technologies and law have settled a bit, the Supreme Court gets involved. Author Orin Kerr, the William G. Simon Professor at the University of California, Berkeley Law School, presents a framework for adjudicating digital searches and seizures in The Digital Fourth Amendment: Privacy and Policing in Our Online World, published by Oxford University Press. His approach, equilibrium-adjustment, “takes the legal rules that existed before the technological shift as a starting point, and it asks how to preserve the values served by those rules amid the gale-force winds of technological change.”

Background
Professor Kerr’s book reinforces his status as a leading law professor and Fourth Amendment theorist—it provides a thorough background in privacy law, starting back in Entick v. Carrington, a 1765 decision from the English courts proscribing overly broad warrants, and continues through foundational cases in U.S. jurisprudence such as Katz v. United States (1967), which addressed placing a microphone on the outside of a telephone booth, as well as United States v. Knotts (1983) and United States v. Karo (1984) that dealt with beepers hidden in five-gallon drums of chemicals used in drug production. The Supreme Court found that tracking the beepers in public did not violate the defendant’s privacy expectation but did as soon as the devices moved inside a home.

I appreciate the thoroughness and efficiency of Kerr’s background coverage. Specifically, he resists the temptation to mention prominent cases such as Griswold v. Connecticut (1965) that aren’t on-point for this argument and saves space for more relevant citations.

Local Devices
Part II addresses local devices such as computers and mobile phones, presenting Kerr’s arguments for how courts should adjudicate searches and warrant requirements based on his equilibrium-adjustment paradigm. After presenting valuable background on how these searches are conducted (usually by creating an image of the device, if possible), he argues for his preferred interpretation of searches in light of how the enormous storage capacity of a digital device compares to the traditional paper filing system on which Fourth Amendment jurisprudence evolved.

Part III moves on to networks and the third-party doctrine, which states that information freely exposed to a third party, such as the address on the outside of an envelope or numbers dialed on a phone network, can be accessed routinely by law enforcement. Other topics include the use of a GPS tracker placed on a defendant’s car, as was examined in United States v. Jones (2012); automated license plate readers; and pole cameras installed near a place of interest to provide sustained surveillance. Per that last point, through his Bluesky account Professor Kerr shared an 11th Circuit Court ruling that 10 months of such observation didn’t constitute a search because the areas surveilled were in public view.

A Vague Standard at Best
Kerr devotes all of Chapter 9 to Carpenter v. United States (2018) because of its seismic impact on the digital Fourth Amendment. The opinion found that requesting cell-site location information (CSLI) from a mobile services provider required a search warrant for…reasons. The lack of a concrete rule for lower courts to follow has caused “deep uncertainty” and led to courts proceeding cautiously. To remedy that uncertainty, Kerr proposes a three-element test to determine if a warrant is required:

• The records must be of a new type made available by the digital world.
• Generating the records must be unavoidable.
• The information must be from the kinds of records that reveal the privacies of life.

These tests are simple to state but require significant interpretation and analysis. I plan to revisit his discussion in the near future and believe this chapter offers substantial insight for me as a non-lawyer but especially for attorneys and judges addressing these issues.

Moving Forward
The remainder of The Digital Fourth Amendment discusses matters at the forefront of the law, including government buying data from private sellers, geofencing warrants gathered from Google Maps and similar services, and the “unanswerable questions” of what Kerr calls mosaic theory as argued in United States v. Maynard (2010), a companion case to United States v. Jones. The DC Circuit’s ruling in Maynard found that tracking a car briefly using a GPS device would not constitute a search, but 28 days of such tracking without a warrant allowed the authorities to create an “intimate picture” of the defendant’s life that was not reasonable to allow.  While the Massachusetts Supreme Judicial Court has wholeheartedly embraced mosaic theory, Kerr isn’t convinced of its utility because it seems impossible to draw a bright line demarking where a collection of data points taken in aggregate crosses into areas protected by the Fourth Amendment.

Conclusion
I believe The Digital Fourth Amendment provides an outstanding summary of the state of play in Fourth Amendment jurisprudence. In addition, Professor Kerr’s paradigm of equilibrium-adjustment offers a path forward as technology changes. While new laws and Supreme Court decisions (should they ever decide another Fourth Amendment case) will shift the playing field, one could do much worse than using equilibrium-adjustment to maintain the existing value structure.

One might ask whether equilibrium-adjustment is required…in many ways it seems obvious and merely a description of the status quo. I believe the paradigm might seem obvious in hindsight but laying it out explicitly is useful. In the second edition of Legal Argument: The Structure and Language of Effective Advocacy, James A. Gardner writes that “the judge wants nothing more than to be led out of this jungle by a confident, reliable guide . . . .” I believe Professor Kerr has provided such a guide though we can expect the specifics to be debated for years to come.

Stadium Naming Rights

Through my company Technology and Society, Incorporated, my wife Ginny and I sponsor London Seaward, a London-based women’s football (soccer) club that plays in the Women’s National League Division 1 South East (Tier 4). The 2024/25 season will be our third time around with the club—we can’t wait to see what’s in store!

There has been a fair bit of offseason turnover on the coaching and player fronts, but the new staff is in place and there’s a solid core ready to move forward. Seaward continue to benefit from a long-term groundshare agreement with Redbridge FC, offering a stable base from which to operate. The 2022/23 season was difficult, with their home ground forcing Seaward to sign a series of eight-match contracts without assurances they would be able to play all of their games at the same venue. Redbridge’s generous terms put that uncertainty firmly in the rear-view mirror.

When you alight at Barkingside station on the Central line and make the short walk on Station Road to the stadium, you’ll also see something new: a 3G artificial turf pitch that was just installed. The new, durable surface will reduce match postponements due to weather; provide a more reliable and predictable schedule for players, staff, and fans; and serve as a valuable community resource.

You will also notice that the stadium has a new name: techsoc.com Stadium at Oakside. Redbridge invited my company to join the backers group funding the transition; while I will receive some return on my investment, I believe the arrangement should acknowledge and reward the work that Redbridge have put into their club and facilities over the years. Naming rights offer meaningful non-monetary compensation, for which I’m grateful.

Joining the Team

When I spoke with my lead UK attorney, she wondered why in the world I cared about a couple of football clubs (actually three, including Newbury Forest) in east London. I’ve written about how I discovered London Seaward when their vice-chair put out a call for support on (then) Twitter after the club had been cut loose with almost no notice by their big-name men’s club, but I’ll reiterate that the players’ determination to make a go of it as an independent club in a league with Queens Park Rangers, Norwich, and Cambridge United on limited funds spoke to me. My own experiences competing against huge schools from northern Virginia on a Rockingham County Public Schools budget meant I had no end of empathy for Seaward’s position.

London real estate is expensive, especially when you consider that east London is historically one of least-resourced parts of the capital region. While there is more space for park pitches as you move away from central London, the lack of pitches that can be used in most weather conditions is down to the lack of funds (and will) to make them happen.

Redbridge FC had the will to assemble a team to fund their stadium’s upgrade to 3G. No one involved, me included, had the cash to pay for the upgrade individually but together we could make it happen.

Creating Shared Value

Does helping to fund Redbridge’s pitch upgrade make financial sense? Not really…I could make the same amount of money risk-free by investing in U.S. government bonds. What it does, however, is create a community resource that benefits Redbridge in particular and east London in general by adding another pitch for use by all members of the community.
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Michael Porter advanced the concept of corporate social responsibility, where a company uses its resources in selected ways to support community initiatives the company favored. Later, Porter and co-author Mark Kramer advocated for an approach they called “creating shared value”. As they stated in a 2011 Harvard Business Review article:

The new 3G pitch does just that. Yes, Redbridge will benefit from the rents they earn from matches, practices, school trips, and corporate events, but they will also make the techsoc.com Stadium available for community groups. They put in the groundwork (literally) for this effort, so they should reap most of the reward.

Porter and Kramer further note that shared value is about “advancing the economic and social conditions in the communities in which [the company] operates.” As a course creator and speaker whose products are available worldwide, I could claim that I “operate” in east London, but the reality is that my sponsorship of London Seaward and forgone revenue sharing in the 3G pitch upgrade will never be paid back in full. That’s OK…I’m doing fine. What’s more, Ginny and I have dedicated resources to helping a community that deserves to have a place to gather, play, and compete.

Conclusion

I like to joke that my philosophy of life is “Think globally. Act randomly.” but there’s real benefit in looking beyond one’s immediate surroundings for places to make a difference. Ginny and I still support local groups such as White Bird Dance and the Many Hats Collaboration, but the opportunity to support London Seaward, Redbridge FC, Newbury Forest, and east London in general offered a way to provide significant benefit to a community we’ve come to care about a great deal.

I like to think I learned something from the baseball field provided as a community resource by the Ruritan Club in Mt. Crawford, Virginia. Just as people in a small town in the shadow of the Appalachian Mountains need a place to gather and play, so do their counterparts in east London. Now both communities have that place.

Another season of football (soccer) is in the books and London Seaward finished eight of twelve, with their 29 points well clear of the relegation zone and a solid mid-table performance. There was a rough patch in the middle of the season where Seaward faced a long string of higher-division opponents and other Tier 4 clubs who were undefeated at the time and/or ended up winning their league, but that run included Seaward’s first cup win over a Tier 3 opponent. It was a thrill to see that win and to watch the club right the ship and remain comfortably at Tier 4.