prior probability

In our previous post, we restated Ron Allen and Mike Pardo’s “relative plausibility” theory of legal proof (or what Allen and Pardo also call the “explanatory account” of evidence), an approach meant to displace probabilistic or mathematical theories of legal evidence. Briefly, according to Allen and Pardo, jurors don’t engage in highfalutin probabilistic reasoning when they decide civil or criminal cases. Instead, they simply compare and contrast the stories of the plaintiff and the defendant, and the party who offers the best explanation of the evidence—i.e. the party with the best* story—wins. (*Of course, the meaning of “best” in any given case will depend on the burden of proof used to decide the case, such the preponderance standard in civil trials or the reasonable doubt standard in criminal ones.) Continue reading →

As we mentioned in a previous post, law professors Ron Allen and Mike Pardo summarize and critique probabilistic theories of evidence on pp. 7-12 of their most recent paper “Relative plausibility and its critics.” (Hold on: “critique” is too polite. They launched a blistering attack!) In addition, they also present an attractive and intuitive alternative theory of legal trials in their paper. Without further ado, here is how they describe their theory of  “relative plausibility” in their own words (pp. 13-14, footnotes omitted):

“Rather than characterizing proof standards as probabilistic thresholds (such as 0.5), [our theory of] relative plausibility accounts for the standards in terms of explanatory thresholds. The proof process involves two stages: (1) the generation of potential explanations of the evidence and events, and (2) a comparisons of the [plaintiff’s and defendant’s competing] explanations in light of the applicable standard of proof. In general, the process depends on the parties to obtain evidence and to offer what they consider to be the best explanation (or explanations) that support their respective cases. *** The explanatory thresholds vary depending on the standard—with higher standards requiring a higher threshold. Under the ‘preponderance of the evidence’ standard, fact-finders determine whether the best of the available explanations favors the plaintiff or the defendant. The best available explanation will favor the plaintiff if it includes all of the legal elements of plaintiff’s claim; it will favor the defendant when it fails to include one of more elements. A number of general criteria affect the strength or quality of an explanation. These criteria include considerations such as consistency, coherence, fit with background knowledge, simplicity, absence of gaps, and the number of unlikely assumptions that need to be made.”

This relative plausibility theory of legal proof is itself very plausible and intuitive. Alas, this theory does not banish the specter of probability from the trial process, for the word “best” is just code for “more probable”, whether we assign a numerical value or not to describe the level of a story’s plausibility! (See image below, by way of example.) Stay tuned, we will weigh the pros and cons of Allen and Pardo’s relative plausibility theory in our next two blog posts …

CNN, the first television channel to provide 24-hour news coverage, went on the air on this day in 1980. At the time, CNN’s format was a radical innovation. Today, with the rise of the Internet, CNN–and cable TV generally–seem so antiquated …

We recently discovered Ron Allen and Mike Pardo’s new paper on “Relative plausibility and its critics” via Larry Solum’s Legal Theory Blog. Because of our fascination with all things Bayesian and with the role of probability theory in legal trials, this 71-page, single-spaced paper is a must-read for us. In their paper, Allen (pictured below, left) and Pardo (right) criticize probabilistic theories of juridical proof and then present an alternative “relative plausibility” theory of legal proof. In this post, we will summarize Allen and Pardo’s main criticisms of probability theory in law: Continue reading →

In addition to Frank Valdes and Margaret Montoya, our friend and colleague Tayyab Mahmud (Seattle University School of Law) also attended the first annual Margaret Montoya Legal Scholarship Retreat at Campo Sano in Central Florida. Here are a few things we learned from Professor Mahmud, who shared his thoughts on the politics of scholarship:

1. Academia’s Golden Rule. Among many other pearls of wisdom, Professor Mahmud shared one of the most important bits of scholarly advice we have ever received: “To be taken seriously, one must take the work of others seriously.”
2. Every law has an exception. Beginning with the famous Roman law maxim necessitas non habet legem (“necessity knows no law”), every legal doctrine, rule, or principle always has an exception or outer limit. Indeed, not only does every rule have an exception; it is the exceptions that tell you what the rule really is!
3. What metaphorical Kool-Aid are you drinking? According to Wikipedia, the phrase “drinking the Kool-Aid” is an idiom or popular expression that refers to a person or group who goes along with a doomed or dangerous idea because of peer pressure. (The quote below by actress Kat Dennings captures this idea perfectly.) In Academia, the “Kool-Aid” might refer to one’s theoretical paradigm or to the hidden assumptions that one simply accepts as true instead of subjecting to rigorous examination.

Our friend and colleague Frank Valdes (University of Miami) also attended the first annual Margaret Montoya Legal Scholarship Retreat. He shared his thoughts on the craft of scholarly writing during the retreat. Here are a few things that we learned from Professor Valdes:

1. There are puzzles, and then are Puzzles. Most scholarship is problem-solving. Some problems consist of puzzles (small p), problems that we have already solved in our minds. Our solution might be a tentative one, or it might be fully-developed. In either case, the purpose of our scholarly writing is to share our pre-arranged solutions with our readers. Other problems, by contrast, consist of Puzzles (capital P), problems we have no idea how to solve ahead of time. In these cases, writing is a form of discovery.
2. Cultivate your scholarly garden every single day. There is no algorithm for deciding what problems or puzzles/Puzzles are worth working on, but you must work on your problems every single day. This work might consist of studying the existing literature on one of your problems. Or it might consist of writing a paragraph or an entire page about some aspect of one of your problems. Or it might consist of editing a passage or page you have already written. Whatever the case, there are no short cuts. One must allocate sufficient time each day to one’s scholarly projects and problems. (This will be the time when you close your door, shut off your email, and just work.)
3. It doesn’t have to be perfect; it just has to be done. When do you know a particular project of yours is done? Ideally, it’s when you feel you have said something original or novel about the problem you are working on …

<<Under normal conditions the [legal scholar] is not an innovator but a solver of puzzles, and the puzzles upon which he concentrates are just those [that] he believes can be both stated and solved with the existing [legal] tradition.>>

We will continue blogging about the Margaret Montoya Legal Scholarship Retreat in the next few days.

As we mentioned in our previous post a few days ago, we have been attending the first annual Margaret Montoya Legal Scholarship Retreat at “Campo Sano” in a rural part of Volusia County, Florida. The WiFi connection was pretty bad out there, so we decided to disconnect from the Internet during our visit to Campo Sano. In this post, we will share three new things/insights that we learned from Professor Margaret Montoya during the retreat:

1. Lawyers, judges, and law professors are storytellers, so what stories do you want to tell? When a lawyer argues a case, or when a judge decides a case, or when a law professor writes a scholarly paper, they all usually begin by telling a story, such as the facts of the case under discussion. There are many types of stories and many ways of telling the same story. Good legal scholars are not only good storytellers; they are also able to find deeper meaning and connections between law and these stories.
2. Always ask yourself ahead of time, Who are you writing for? If you are a pre-tenure law professor, one of your audiences is going to be your tenure committee! How much this brute fact constrains the type of scholarship you want to engage in or the types of stories you want to tell may vary from university to university, but it’s always a good idea to consider ahead of time the scholarly reputation you want to develop.
3. Who did you leave out of your footnotes or end notes? In legal scholarship, who you don’t cite says as much about your scholarship as who is cited in your work. Whatever the specific legal field you are writing in, it is essential to acknowledge those who came before you …

Credit: Jane Hope

We are attending the first annual Margaret Montoya Legal Scholarship Retreat at “Campo Sano” (see image below) in Volusia County, close to Deland, Florida. More details to follow …