Since I'm sitting in DC right now and you aren't, do you think that one cause of the drop in murders might be the systematic destruction of the "hood" in DC?
Specifically, DC has literally plowed under the area south and east of Capital Hill and put a Baseball stadium, office buildings and high rent condos there instead.
Also, in North East, a new government corridor is being erected and all the previous housing projects etc. were knocked down. The new government office buildings are being interspersed with Loft Apartment buildings. Again high dollar.
The "bad part of town" is being systematically squeezed into a more and more remote area mostly across the Anacostia river from the rest of DC.
Where have all those people gone? Mostly to Prince Georges County. Why don't you do some research on how fast the murder rate has grown in PG County in the last 15 years?
Now, just accept that your statistics are a meaningless post hoc ergo proctor hoc fallacy!