I think there is a very high chance of him retaining his driving license. His teaching license perhaps not, there may be some sort of "discretion" process there to see the revoking of it, but the possibility of him being convicted of drink driving is slim to none. No breathalyser, no blood test no nothing at the time of the alleged crime. They *could* go back and try and find the beers - doesn't mean he drank any in the eyes of the law though. All there is, is one civilians accusation faced with another's probable denial. There is no way anyone could categorically prove he was over the limit at the time, other than a single civilian witness which does not put it beyond reasonable doubt - thus no conviction I'm afraid unless he admits to it.