Answer
Emma Pierson and her colleagues used a method called "regression discontinuity" to examine the evidence and demonstrate that law enforcement officers were motivated by racial bias when they stopped and searched cars. This method allowed them to compare the outcomes of searches conducted by officers who were just above and just below the threshold for making a stop, and showed that officers were more likely to stop and search cars when the driver was Black, even when the officers were just below the threshold for making a stop.