The lifecycle of judicial bias

How does judicial bias arise and persist in the legal system? We trace the lifecycle of judicial bias in India's criminal courts, leveraging the quasi-random assignment of judges to courts and cases. We first document substantial variation in bias: within the same court, assigning a same-religion defendant from a judge at the 25th to 75th percentile of bias increases acquittal probability by 7.5 percentage points, 45% of the mean acquittal rate. We then examine how different triggers across judges' professional careers affect their bias. Exposure to Hindu-Muslim communal riots during a judge's first five years of service leads them to increase same-religion acquittal rates by 17.5%. Yet, judges who work alongside colleagues from different-religions during this critical period show no such effect. Next, social interactions between judges reinforce judicial bias. On-the-job exposure to biased colleagues leads judges to reduce acquittal rates for defendants of different-religions by 3.2 percentage points, with effects that persist for over a year. These findings suggest that judicial bias is neither innate nor inevitable, but rather shaped by experiences and relationships, and that thoughtful institutional design can prevent and mitigate discriminatory practices across various professions.