The largest-ever study of alleged racial profiling during traffic stops has found that blacks, who are pulled over more frequently than whites by day, are much less likely to be stopped after sunset, when “a veil of darkness” masks their race.
That is one of several examples of systematic bias that emerged from a five-year study that analyzed 95 million traffic stop records, filed by officers with 21 state patrol agencies and 35 municipal police forces from 2011 to 2018.
The Stanford-led study also found that when drivers were pulled over, officers searched the cars of blacks and Hispanics more often than whites. The researchers also examined a subset of data from Washington and Colorado, two states that legalized marijuana, and found that while this change resulted in fewer searches overall, and thus fewer searches of blacks and Hispanics, minorities were still more likely than whites to have their cars searched after a pull-over.
The research team includes Sam Corbett-Davies, a 2016 Karr Family Graduate Fellow, Computer Science.