When a police officer pulls over a driver, there are many reasons why he might try to initiate a search — maybe the driver is acting suspicious; maybe there are signs of drugs or an illegal gun.
Or maybe the driver is just black or Hispanic.
That’s the troubling conclusion of a new paper by Camelia Simoiu, Sam Corbett-Davies, and Sharad Goel at Stanford University, which evaluated the threshold that police use to search white, black, Hispanic, and Asian people in North Carolina. They found that the threshold used for black and Hispanic people was much lower than the threshold for their white and Asian counterparts.
To do this, the researchers put together a data set of 4.5 million traffic stops in North Carolina. They then ran this data set through a mathematical model developed for the study, which analyzes police officers’ average threshold for a search by looking at the race of a driver, the department of the officer making the stop, whether the stop resulted in a search, and whether a search turned up drugs, guns, or other contraband.
In nearly every one of the 100 [police] departments we consider, we find that black and Hispanic drivers are subject to a lower search threshold than whites, suggestive of discrimination against these groups. In many departments, we find the disparity is quite large, with the threshold for searching minorities 10 or even 20 percentage points lower than for searching whites. For Asians, in contrast, the inferred search thresholds are generally in line with those of whites, indicating an absence of discrimination against Asians in search decisions.
According to the study, if white and black drivers were held to the same standard, there would have been more than 30,000 fewer searches of black drivers (or one-third of searches of black drivers) and 8,000 fewer searches of Hispanic drivers (or more than half of searches of Hispanic drivers) over the six years in the data set.
The findings stood when the model checked for variations in the year, time of day, age, and gender. Across all these variables, Hispanic and black drivers were held to a lower standard before cops initiated a search.
There are several important caveats to the paper. For one, it’s the first time this new mathematical model has been used — and it will need much more study to know just how reliable it is. The results are also only for one state, so it’s not clear if they apply nationwide.
The researchers also caution that they can’t definitively conclude that the differences between races are entirely motivated by racial bias: “For example, officers might instead be applying lower search thresholds to those from lower socioeconomic backgrounds, a demographic that is disproportionately black and Hispanic. At the very least, though, our results indicate that there are concerning irregularities in the search decisions we study.”
But there’s reason to believe these findings are onto something. Multiple studies and investigations have found, for example, that police are more likely to search black and Hispanic people than their white peers, even though searches of black and Hispanic drivers are less likely to turn up contraband. That suggests that cops are searching too many minority drivers, picking up a lot of innocent people along the way.
The study puts a different spin on this type of data, potentially showing yet another way minority Americans are overpoliced.