December, 2006. An independent study commissioned by the Metropolitan Police Department has found no evidence that MPDC officers engage in racial profiling when conducting traffic stops.
The study, designed andconducted by Lamberth Consulting, national experts on racial profiling research, examined data collected at 20 locations throughout the District between February 2005 and January 2006. The final report concluded there was “no evidence of targeting of either Blacks or Hispanics in Washington, DC by the MPD. The proportion of Black and Hispanic motorists stopped at the 20 locations was virtually the theoretically expected outcome based upon their presence in the transient population.”
Chief of Police Charles H. Ramsey ordered the study as part of the Biased Policing Project, an MPDC initiative that Ramsey started in 2002 to examine whether there is any bias in the delivery of police service in DC.
“This report confirms what I believed to be true all along: that Metropolitan Police officers are not engaging in racial profiling or other forms of biased policing in their traffic enforcement,” said Ramsey, who retired on Thursday after leading the MPD for nearly nine years. “Our officers take very seriously their responsibility to serve and protect in a fair and bias-free manner, and I am proud of their hard work and integrity,” he added.
The MPD study is different from other racial profiling analyses that have used a simple comparison between the race and ethnicity of motorists stopped by the police and the makeup of the resident population of a jurisdiction. Lamberth’s study followed a more sophisticated and rigorous methodology that has been relied upon by the courts.
“The methodology employs what we believe to be the only appropriate benchmark for such an analysis; that is, a direct measure of the transient population (driving populations and pedestrian populations) in specific locations,” Dr. Lamberth wrote. “This allows a comparison of the racial/ethnic groups as they are represented in the transient population to police stops of those groups at specific locations.” This approach is particularly important in the District of Columbia, in which a large percentage of the motoring public on any given day is from outside DC.
The study used what are called “odds ratios” to determine whether certain racial or ethnic groups were stopped by the police at a rate that exceeds their presence in the transient population at the 20 locations examined. The odds ratio is best understood by filling in the blank in the following sentence: “If you are a Black motorist, you areX times as likely to be stopped as if you are not a Black motorist.” If no racial profiling is occurring, the ratio would be 1.0.
The study concluded that at 12 of the 20 locations, the MPDC stopped fewer black motorists than would be expected in the transient population or the same percentage as would be expected. At the other eight locations, officers stopped black motorists at a slightly higher rate, although most of these had an odds ratio within the range that the researchers considered “benign.” The weighted odds ratio for the MPDC to stop black motorists at all 20 traffic locations combined was 1.0, which is the theoretically expected value.
There were far fewer Hispanic motorists noted in the benchmarking at the 20 locations; in fact, there were just seven locations where there were enough Hispanic motorists to conduct a reliable analysis. The weighted odds ratio for the MPDC to stop Hispanic motorists at these seven locations combined was 1.1, which is essentially the theoretically expected value.
The study also monitored the pedestrian transient population at five locations. At one of the locations, there was a somewhat elevated tendency to over-stop black and Hispanic populations. At another location where whites were a large majority, researchers discovered that black pedestrians were stopped at a rate higher than their presence in the pedestrian population.