I know a case involved a rich teen boy who's had car accidents 3 times in 16 months, and his lawyer got him off hook. The police found drugs and tools in his car, arrested him, but he refused to take blood tests at the time of accidents. So the state prosecutor can't proove that he had the drugs in his body at the exact time of car accident, even he admitted used drug that day. Therefore, can't proove DUI.
So be careful when you cross streets or driving, there are drivers under influence on the roads.