The point is that California is much bigger (And much more populated) than DC. But If you want stats then....
72 divided by 163696 is 0.000439839703. That means 1 murder per about 0.000439839703 for every square mile of california. take 0.000439839703 and multiply it by 68, DC's square miles, and you get 0.029909099804 murders that most likely will happen in DC in 12 days. Of course we round down, and we get 0. (I think) Yes I'm a nerd