The FBI publishes statistics. Your local police departments will also have statistics.
But it gets pretty specific, sometimes almost block by block. In your case, the crime rate in Brookland might be different from the rate in Shaw, or Adams-Morgan, etc. Same with the surrounding areas. The crime rate in Fairfax County might vary depending on whether you're asking about Centreville, Annandale, McLean, or Springfield.
A number that just applies to D.C.--or to Northeast--isn't going to be enough to tell you what you want to know.