The British singer was having a night out at Dublin Castle pub in Camden, London, when she all of a sudden lost it and attacked Wayne Lindsay out of the blue, reports FemaleFirst.
Lindsay was behind Winehouse when she suddenly turned around and shouted an insult at him, and then continued to hit him for no apparent reason.
The man recounted, "She was in front of me at the bar and suddenly turned and smacked me three times across the face."
He added, "She was wild. She just flipped. It was as if she had voices in her head."