October 31, 2017

The causal impact of bail on case outcomes for indigent defendants in New York City

By Kristian Lum, Erwin Ma and Mike Baiocchi


It has long been observed that defendants who are subject to pre-trial detention are more likely to be convicted than those who are free while they await trial. However, until recently, much of the literature in this area was only correlative and not causal. Using an instrumental variable that represents judge severity, we apply near-far matching — a statistical methodology designed to assess causal relationships using observational data¬† –to a dataset of criminal cases that were handled by the New York Legal Aid Society in 2015. We find a strong causal relationship between bail — an obstacle that prevents many from pre-trial release — and case outcome. Speci fically, we find setting bail results in a 34% increase in the likelihood of conviction for the cases in our analysis. To our knowledge, this marks the first time matching methodology from the observational studies tradition has been applied to understand the relationship between money bail and the likelihood of conviction.

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