Priors neutral between the parties: the Batson motion in Idaho v. Ish

Abstract

For Bayesian inference to be useful to a court, it is essential that the priors used should be neutral between the parties. ‘Neutrality’ reflects the idea that the fact-finder would want the statistical analyses to be fair to both parties. It is neither the same as the legal designation of which party has the burden of proof with respect to a particular matter, nor the standard of proof that must be met for that party to prevail. The recent case of Idaho v. Ish raises the question of how to find such priors, particularly in a doubly constrained 2 × 2 table with a zero. This article re-examines this issue. It also offers reflection on whether, given a zero in the table (which here means that all members of a particular race or sex are excluded from jury service), it matters how many are excluded.