Forensic Maths

The Economist’s Prospero Blog features an interview on forensic maths – Coralie Colmez, the author of “Math on Trial: How Numbers Get Used and Abused in the Courtroom” speaks about the use of maths and statistics in a legal context. Most of her examples are drawn from criminal law, but the issues she raises are relevant to everyone who uses maths and statistics in a courtroom or in settlement discussions.

Maths and statistics is a topic that I find, for my sins, fascinating, and “Math on Trial” will definitively be on my reading list.* Iudex non calculat must become a concept of the past, and the earlier, the better. In the United States, there are training programmes for law professors on empirical methods and empirical legal scholar programmes. I hope that this trend will find its way across the Atlantic rather sooner than later. But then, this development has taken its time over there as well: “For the rational study of the law the black letter man may be the man of the present, but the man of the future is the man of statistics and  of economics” – Oliver Wendell Holmes wrote in 1897.

Whenever I use fairly simple and straightforward decision tree analysis, I find that clients love it and connect to it far more easily than to standard forms of presenting legal analysis. However, I recall a case in a court of appeals (Oberlandesgericht) where I spent almost an hour explaining why an 50% chance of success on a legal issue followed by another 50% chance of success on a factual issue equals an overall probability of 25%, and not 50%….

In the interview, I was surprised to read that “[t]here is actually a mathematician called Laurence Tribe who argues that maths shouldn’t be brought into the court room.” I had always thought of Lawrence Tribe as a constitutional scholar and advocate. It turns out he is both – he gained an A.B. in Maths  before embarking on his legal career, and combined the fields for example in “Trial by Mathematics: Precision and Ritual in the Legal Process,” 84 Harvard Law Review 1329 (1971). But even the combined weight of Tribe being a mathematician and an eminent legal scholar does not persuade me that maths should be kept out of the court room – or the law school class room, for that matter.

* Recommended reading: Bernstein, Peter L. (1996). Against The Gods: The Remarkable Story of Risk. New York: John Wiley & SonsISBN 0-471-12104-5.


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