Friday 12 June 2009

Wigmore Evidence Charts

I have been reading a fascinating book by two probabilists Joseph Kadane and David Schum called “A probabilistic analysis of the Sacco and Vanzetti Evidence” about the famous US murder case from the 1920’s.

One interesting feature of the book is their use of a particular type of graphic which they call a ‘Wigmore Evidence Chart’. They also show a complete appendix of these charts summarising the Sacco and Vanzetti evidence. Wigmore was a US jurist who developed a probabalistic approach to proof (he published this approach from 1913 onwards) and is seen by the authors as the earliest exponent of what today are called ‘inference networks’ (Wikipedia HERE).

I have not seen this type of chart before. They are interesting but visually a bit ropey, they could really do with improvements in clarity, line weights, text integration and colours etc.

However, they are not dead; a quick search on Google took me to this 2008 paper by Bruce Hay of Harvard Law School (HERE). The paper is from the journal “Law, Probability and Risk” and the Abstract says the following;

“Wigmore’s `The Problem of Proof’, published in 1913, was a path-breaking attempt to systematize the process of drawing inferences from trial evidence. In this paper, written for a conference on visual approaches to evidence, I look at the Wigmore article in relation to cubist art, which coincidentally made its American debut in New York and Chicago the same spring that the article appeared. The point of the paper is to encourage greater attention to the complex meanings embedded in visual diagrams, meanings overlooked by the prevailing cognitive scientific approaches to the Wigmore method.”

I will be ordering this paper and reading around it, but in the meantime you may find this interesting.

Just found more on Wigmore – a whole book by Anderson, Schum & Twining HERE that has long explanation of how to apply the method.