Leona Lewis. Photo by AP.
Peter Kowalczyk had been charged with punching the pop star in the face as she went to sign his copy of her autobiography in central London on October 14.
Kowalczyk pleaded guilty to common assault.
A judge ordered the 29-year-old to remain in the hospital under mental health laws. Prosecutor Melanie Lee, reading out a witness statement by Lewis, said on Monday the singer felt completely devastated by the attack. In the statement Lewis says: "Now I am very frightened about going out in public."
Lee says the attack left Lewis with a red and swollen face.
