Monday, August 18, 2014

One black person in the jury pool reduces black defendant convictions by 16%

In a great paper, The Impact of Jury Race in Criminal Trials, Shamena Anwar, Patrick Bayer and Randi Hjalmarsson exploit random variation in the jury pool to estimate the effect of race on criminal trials. The authors have data from nearly 800 trials in two Florida counties. On any given day, a jury pool is randomly drawn from a master list based on driver’s licenses. On some days, the pool of about 30 people contains some black members and on other days, purely for random reasons, it does not. The voir dire process—removals, excuses and challenges—whittles down the jury pool to 6 jury members with typically 1 alternate.

The authors have data on the race, gender, and age of each member of the jury pool as well as each member of the ultimate jury. The authors also know the race and gender of the defendant and the charges. What the authors discover is that all white juries are 16% more likely to convict black defendants than white defendants but the presence of just a single black person in the jury pool equalizes conviction rates by race. The effect is large and remarkably it occurs even when the black person is not picked for the jury. The latter may not seem possible but the authors develop an elegant model of voir dire that shows how using up a veto on a black member of the pool shifts the characteristics of remaining pool members from which the lawyers must pick; that is, a diverse jury pool can make for a more “ideologically” balanced jury even when the jury is not racially balanced.
--Alex Tabarrok, Marginal Revolution, on the elusive goal of color-blindness