The Washington Lawyers' Committee for Civil Rights and Urban Affairs presented its study, which analyzed arrest statistics from 2009 through 2011, Friday, The Washington Post reported.
The authors of the report found that eight of 10 adults arrested in Washington are black, and nine of 10 people arrested on the charge of simple drug possession are black. However, only 47 percent of the city's population is black, the study found.
"Police are spending an enormous amount of time resolving behavior that is not life-threatening," said Roderic V.O. Boggs, executive director of the lawyers' group.
The report a month after the American Civil Liberties Union found Washington police were arresting people for marijuana possession 60 percent more in 2010 than 2001.
Meanwhile, Police Chief Cathy L. Lanier said her department has "not prioritized marijuana arrests. Since day one, my priority has been combating violent crime, and the District is safer as a result."