Being an alcoholic is nothing to do with how much a person drinks, It's more to do with why and when. There are a lot of people who drink heavily say at the weekend and then drink nothing during the week, they are not alcoholics. Then again there are people who must have a drink every day in some cases with their cornflakes! They sip booze all day, probably not drinking that much in total, just topping up, they need a drink, they are alcoholics. So on balance I'd say to prove someone is not an alcoholic you would have to ask the person what they would accept as proof. In reality I don't think you can prove it in the legal sense, I mean abstain but how do you prove you've abstained? An alcohilic could at a push abstain for long enough to get a liver test done but start again, that proves nothing. Sounds like a lack of joined up thinking to me.