Study of Racial Profiling in Oakland Finds Mixed Evidence of Bias in Stop Decisions; Evidence of Bias in Searches

For Release

August 24, 2004

A study released today by the Oakland, Calif., Police Department's Racial Profiling Task Force found mixed evidence of whether racial bias was involved in the initial decision by police to stop particular motorists, but evidence of racial bias in certain traffic enforcement actions by police, including weapons searches of motorists stopped by officers.

The study, conducted for the Task Force by the RAND Corporation, analyzed traffic stop information in two different ways, with one finding some evidence and another finding no evidence of racial bias in officers' decision to stop motorists.

The Task Force includes representatives from the ACLU of Northern California, the Citizen Police Review Board, the NAACP, People for a Better Oakland, RAND, PolicyLink, the SCANTRON Corporation and police officer organizations. The group asked RAND to carry out the study as part of a wider effort to develop strategies to prevent racial profiling in Oakland and to assess whether racial profiling is a problem in the city's police department.

The Oakland study marks the first use of a unique statistical tool designed by RAND researchers to provide a better means of analyzing police traffic stop information to determine whether racial profiling is evident.

If racial profiling was occurring, stops for members of minority groups should be higher when officers could determine drivers' race in advance of making a stop, according to researchers. RAND researchers analyzed Oakland traffic stops during a period just before the end of daylight and a similar period just after nightfall — when officers are less likely to be able to identify a driver's race in advance. The researchers found that 50 percent of the drivers stopped during the daytime study period were black, compared with 54 percent during the nighttime period.

“This measurement shows no evidence of racial profiling in the traffic stops made by Oakland police officers during the study period,” said Greg Ridgeway, the RAND researcher who headed the project.

However, signs of racial bias were apparent when researchers analyzed traffic stops based on police officers' own reports of whether they could determine a motorist's race before they made a stop. When officers reported knowing the race of the driver in advance, 66 percent of the drivers stopped were black, compared with 45 percent when police reported not knowing the race of the driver in advance, according to the RAND study.

“The project was an enormous success in that the Department worked collaboratively with the community to address concerns regarding racial profiling,” said Capt. Ronald Davis, Inspector General of the Oakland Police Department. “On one hand, the report validates the professional work of the officers and their commitment to equitable enforcement of the law. At the same time, it highlights potential bias in post-stop activities that will be addressed with the implementation of the newly developed racial profiling policy and through education and awareness.”

“The Department's efforts in data collection and analysis, and its willingness to identify and address its shortcomings, serve as a national model,” Davis added. “We look forward to our continued relationship with the Task Force and we are confident that together we will improve the manner in which police services are delivered to the Oakland community.”

Racial profiling is frequently defined as law enforcement activities — such as traffic stops, arrests and searches—that are initiated solely on the basis of race, unless police are looking for a specific suspect who has been described by race. Police departments around the country have been accused by critics of using profiling to unfairly target law-abiding members of minority groups for closer scrutiny.

The RAND research analyzed 7,607 vehicle stops recorded by Oakland police officers between June and December 2003, examining a variety of variables to look for any evidence that would suggest racial profiling.

Researchers found that blacks were involved in 56 percent of all traffic stops studied, although they make up just 35 percent of Oakland's residential population. But that difference does not necessarily suggest racial profiling, according to researchers.

Efforts to analyze traffic stop data to look for evidence of racial profiling have been hurt by important, but difficult-to-measure factors such as the fact that police patrol neighborhoods at different rates. This increases the chance that residents of high-patrol regions will be involved in police stops, researchers say.

Heavier patrols often target higher crime areas, including many urban communities that include high concentrations of minority groups, such as in Oakland. It is also unlikely that people of different ethnic groups traverse the same streets in the same numbers at the same time, another factor that makes traffic stop data difficult to analyze, according to researchers.

Researchers also studied activities that occur once a motorist is stopped, looking for patterns of racial bias. Since police practices — such as the use of pat searches for weapons — vary considerably by time and location of the stop, researchers compared black drivers with “similarly situated” drivers of other races. Among their findings:

  • Black drivers were slightly more likely to have stops lasting 10 minutes or more compared with similarly situated non-black drivers and similarly situated white drivers.
  • Police officers were slightly less likely to issue black drivers a citation than non-black drivers.
  • Black drivers were more likely to be pat-searched for weapons following a traffic stop than similarly situated white drivers.
  • Officers were more than twice as likely to conduct a probable cause search of a black driver than a non-black driver. Only 18 percent of the searches resulted in an arrest, casting doubt on either the officers' reporting of probable cause or on the reasons a probable cause search was conducted.

Researchers say their findings are somewhat limited given that the study examined a relatively short period of time and they found evidence that the number of traffic stops were seriously underreported, particularly during the first four months of the study period.

In addition to an analysis of the traffic stop data, the report discusses steps that the Oakland Police Department has taken to reduce racial profiling, including the development of a comprehensive policy prohibiting racial profiling. The policy not only clearly defines and bans the practice, but also prohibits officers from conducting arbitrary consent searches and requires officers to advise individuals that they have a right to refuse the search.

The Oakland Police Department's Racial Profiling Task Force was created by the Department to address concerns from the community about the issue. The effort has worked to address such concerns and to provide a venue for all sides to learn more about the issue of racial profiling.

The Oakland Police Department began to voluntarily collect traffic stop information in 2000. A grant to the Department from the U.S. Department of Justice provided the funding for the RAND analysis of the traffic stop information from 2003.

The data used for the racial profiling study was collected using tools developed by SCANTRON Corporation.

About RAND

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