A potential miscarriage of justice re domestic violence.?

My man has been accused of one incident of domestic violence by his alcoholic ex. She is always drunk and staggering down the street with cans. He finished with her because of her drinking and ociated behaviour. He vehemently denies the allegation and I believe him. I've had no concerns about him whatsoever and have seen no evidence of anger, temper, alcohol misuse, etc. He gets on well my with teenagers who would drive anyone demented. He is pleading not guilty. What are his chances of a not guilty verdict?