DURHAM -- Researchers who conducted a study to assess disparities in the race of drivers pulled over by Durham police during daylight hours here stand by their report.
RTI International researchers completed the independent, self-funded “Veil of Darkness” study in March.
Demographic data from more than 151,000 traffic stops by the Durham Police Department from January 2010 to October 2015 was analyzed by RTI researchers during a five-month period.
Researchers evaluated stops during an “intertwilight” period between 5 to 9 p.m. when it is light during some months, but dark during other months.
According to the Veil of Darkness study, the odds of the driver being a black male were 20 percent “higher when the traffic stop occurred during daylight.”
Durham City Council members were presented with a separate International Association of Chiefs of Police (IACP) report during an Oct. 6 work session.
The IACP report evaluated historical data, reports, annual reports, numerical data, computer-aided dispatch data, internal reports and includes interviews with sworn staff, non-sworn staff and community members.
Within the 244 pages of that report, references question RTI’s Veil of Darkness study on pages 186-187.
“The authors of this study stated they ‘found evidence of racial disproportionality in traffic stops conducted by the DPD,’” the IACP report states. “We believe this very broad statement is a misrepresentation and overstatement of the facts, and that the approach used by RTI has material flaws, which cast significant doubt upon their findings.”
During the council’s work session, Mitchell Weinzetl, assistant director of education for the IACP, said the RTI study has “material flaws when held up to research scrutiny.”
The IACP report states the RTI study finds no evidence of racial disproportionality related to female drivers, does not find evidence of racial bias among traffic stops conducted by dedicated traffic units or examining hours of operation by specialized units, and contains no evidence of analyzing race of drivers within each geographical area within the city at various times of the day, or in areas of intentionally higher concentrations of police deployments.
“In fact, the authors make a vague reference to this issue as a limitation of their study,” the IACP report states.
Travis Taniguchi, is a research criminologist at RTI and the study’s lead author.
“Like any methodology, it is not without its limitations,” Taniguchi said. “These limitations, however, are highlighted clearly in the original report, and we make no claims beyond what the data and methods are able to tell us.”
The time period for traffic stops within the study “avoids issues of vastly different driving populations that may be on the road in daytime and nighttime,” he said.
Times of the day are compared throughout the analysis, he said.
Researchers of the RTI report stand behind the methodology, implementation of DPD’s data and conclusions from the analysis, Taniguchi said.
The IACP report, he said, raises issues about the study’s methodology stemmed “from a fundamental misunderstanding of the processes employed.”
The study avoids traditional methodologies requiring benchmarks, Taniguchi describes as problematic, such as the percentage of a minority residents in area to serve as a comparison of those who are stopped by police
“Because we are comparing citywide traffic stop data at different points in time, there is no need to specify an external benchmark that varies by location,” he said.
Concentrating on police deployment is irrelevant, the study centers “on a conceptual argument that officers can more readily determine driver race during daylight than in darkness, Taniguchi said.
Durham council members defended the RTI report during their workshop meeting earlier this month.
Councilman Don Moffitt pointed out the RTI report was initiated by the Durham Police Department.
“The results of that study show the actual biased, and DPS commands released the report … they released the report and they acknowledged the results, and they accepted the challenge of of addressing the issue head on,” Moffitt said.
Councilwoman Jillian Johnson said she disagrees with any suggestion that the racial disparity studies are invalid.
“I think that the people who did those studies, who are a Ph.D. social scientist at UNC, and RTI -- which is one of the most well-respected social science research firms in the country -- are in a good position to tell us whether our data indicates racial bias or not,” she said.