Pretextual Traffic Stops and Racial Disparities in their Use.

A moving-violation traffic stop is pretextual when it is motivated by suspicion of an unrelated crime. Despite concerns that they infringe on civil liberties and enable discrimination against minority motorists; evidence on the use, frequency, and nature of pretextual stops is mostly anecdotal. Using nearly a decade's worth of traffic citation data from Louisville, KY, I find evidence suggesting that pretextual stops predicated on a particular moving violation—failure to signal—were relatively frequent. Compared to stops involving other similarly common moving violations, where arrest rates range from 0.01 to 0.09, stops involving failure-to-signal yield an arrest rate of 0.42. More importantly, pretext to stop a vehicle requires only one traffic violation. In stops involving failure-to-signal, the arrest rate is 0.52 when no other traffic violations are cited, and the presence of other traffic violations yields a 55% relative decrease in the probability of arrest. Relative to conventional traffic stops, black and Hispanic motorists account for a disproportionate share of likely pretextual stops. Yet, within likely pretextual stops, they are arrested at a significantly lower rate than other motorists. Following departmental adoption of body-worn cameras (body cams) I find that the arrest rate in likely pretextual stops increases 33-34%, and the racial disparity in the arrest rate becomes much smaller and statistically insignificant.