get away scotch-free
Refers to your not being charged and/or incarcerated for an indiscretion, due to whether or not you'd consumed alcohol during the period when you'd committed said crime.
Believe it or not, being intoxicated can sometimes actually be a defense in a criminal case, especially if the culprit merely committed a misdemeanor instead of something more serious... if he was drunk at the time, he can often get away scotch-free! Disgusting, but true.