Originally Posted by W.E.G.

Don't leave any articles in plain sight in your parked car in DC.
Even in the daytime.
Even if its a $5 pair of chinese sunglasses.

Anything at all will be classified as a "prohibited weapon" if the investigating officer feels you used it for an "unlawful" purpose. You will be charged with Possession of a Prohibited Weapon (subsection B) of the DC Code. For instance, you could be charged with PPW (bottle).
DC Code - SS 22–4514. Possession of certain dangerous weapons prohibited; exceptions.

Use Waze at all times while driving in DC. Otherwise, I can just about GUARANTEE you will earn a $100-minimum photo radar ticket. The camera on K street under Washington Circle (25 mph limit) hands out about EIGHT MILLION DOLLARS worth of tickets each year all by itself. That's before you count the tickets handed out by the other radar cameras and red-light cameras. They are in all the "gotcha" spots and in none of the spots where dangerous speeding is a genuine public hazard.