Reminds me of someone I knew that would keep a pint of Jack in his trunk. He drove drunk constantly and it was there for when if he ever got into an accident he was prepared to run out of the car, pop the trunk, and pound the bottle in front of all the witnesses.
Can't prove he was drunk at the time of the accident.
I know I’ve read of at least one successful case where the person fled the scene and went home, then claimed he was drinking at home. Honestly, though, there’s so many things that factor into whether an individual gets arrested or released that we’d need more examples to differentiate between just letting someone go and This One Simple Trick Judges Hate.
It's up to the police to show you were driving while intoxicated. You have witnesses corroborating that you were drinking after the accident. Any field sobriety, or blood test they give you would be worthless because it would be after that.
You might not be able to prove it, but anyone willing to chug alcohol in front of witnesses to have that kind of plausible deniability can easily be assumed to have already been drunk to start with. That just doesn't seem like it would hold up to the 'reasonable doubt' standard...