RTI International disputes a recent Durham Police Department consultant’s report that calls the Research Triangle Park nonprofit’s analysis and finding of police bias flawed.
In a four-page letter to City Manager Tom Bonfield and Police Chief C.J. Davis, RTI research criminologist Travis Taniguchi defended the report that looked at traffic stop by day and night and found racial disparities.
“The veil of darkness analysis has been used on data from dozens of jurisdictions and reported in at least six peer review publications,” the letter states. “It is widely considered one of the best available methods for understanding and exploring potential racial disparity in traffic stop data.”
The Oct. 14 RTI letter follows a 244-page International Association of Chiefs of Police report analyzing the Police Department that was presented to the Durham City Council on Oct. 6.
The report concluded the RTI research “has material flaws, which cast significant doubt upon their findings.”
On Monday, Mitch Weintzetl, the association’s assistant director of education, said he hadn’t reviewed RTI’s concerns and couldn’t comment immediately.
The RTI analysis, which was sought by the Police Department and released in March, compared 151,701 traffic stops from January 2010 through October 2015 and found the odds of a traffic stop involving a black motorist were 12 percent higher during daylight hours compared to when it was dark.
Among male drivers only, the odds a driver was black were 20 percent higher when the driver was stopped during daylight than when stopped at night, when presumably the police could not see the person’s race, according to the study by RTI International.
The RTI study found greatest racial “disproportionality” when drivers were stopped by the police department’s HEAT or High Enforcement Abatement Team, which focuses on drugs, vice and gang violence. It found no such pattern within the traffic unit, which stops drivers for offenses such as speeding and driving while impaired.
The IACP report said the report’s finding of evidence of “racial disproportionality is a misrepresentation and overstatement of the facts.”
The IACP report noted the relationship between daylight and the color of the driver was not significant in the 2014 and 2015, when RTI also noted the disparity had largely disappeared.
Taniguchi wrote in his letter to city officials that the disproportionality decreasing over time does not mean that it didn’t exist, but corresponds to changes in training and procedures.
The IACP report also points out no analysis occurred on the race of drivers within a geographic region.
A geographic denominator isn’t needed, Taniguchi said, because they used time and light and the changes over time.
RTI reviewed traffic stops between the 5:30 and 9:30 p.m. “veil of darkness” hours and then used statistical modeling to predict how many black drivers would be stopped versus white drivers. Absent bias, one would expect the same ratio during daylight as during the night, according to the report.
In his letter to city officials Taniguchi wrote that other, more traditional methodologies that use an external benchmark, such as the percentage of minority residents in an area, are problematic.
“In closing, we find no validity in the criticisms leveled by Dr. Weintzetl and believe that the IACP has made fundamental errors in their criticisms of RTI’s analysis, “ Taniguchi’s letter states. “We stand behind the methodology, its implementation of DPD data, and the conclusion drawn from the analysis.”