Veil of Darkness test for racial bias

In the test’s simplest form, researchers compare stops made during the day with stops made at night. If drivers of a particular race were less likely to be pulled over when it was dark, when race is presumably harder to see, that could be evidence of bias.

A typical test This test often analyzes stops from a specific block of time that has both night and day stops, such as only between 5 and 9 p.m. This controls for variables that could influence the results like people’s behaviors during certain parts of the day.

A questionable approach The San Diego County Sheriff’s Department compared stops made during the period of 5-9 p.m. to stops made during the other 20 hours of the day. This method would not be able to determine the presence of racial bias.