Differential prediction and disparate impact of pretrial risk assessments in practice

Abstract

Objective Conduct a multi-site, retrospective investigation of predictive bias and disparate impact post-implementation of the Indiana Risk Assessment System-Pretrial Assessment Tool (IRAS-PAT).Methods Black and White defendants who received IRAS-PAT assessments (n = 2,570) were matched to two comparison conditions (n = 1,527 and n = 3,107) of defendants who did not receive assessments. Area under the curve statistics and multivariable logistic regression models tested for predictive bias. Weighted, multivariable mixed-effects models examined effects of assessments on release decisions by race.Results IRAS-PAT assessments produced lower levels of predictive validity for Black defendants relative to White defendants. Although there were disparities in pretrial release rates, bond amount, and days in detention, there was no evidence that effects of pretrial risk assessments differed by race.Conclusions Even a tool producing biased assessments of risk can improve pretrial release outcomes for defendants irrespective of race and relative to practice as usual.