If you've got arrest or incident data from the Metropolitan Police in Washington DC, and that data is broken out by police district or public service area, you may want to compare it with the racial and ethnic makeup of the people living in those zones.
If so, this post is for you.
The US Census doesn't break out populations by police districts. But in DC and other large cities, census blocks serve as atomic units that usually do fall within police precinct boundaries. So by knowing which blocks are within which districts, you can calculate the populations. Unfortunately, block-level data is only available from the decennial count, so the latest data is from 2010.