The six classic signs of demonic possession are the following.
>An aversion to the sacred
Vehement aversion to any religious iconography, irrational fear of Churches, holy water, priestst and most importantly aversion to Holy Eucharist.
>Abrupt knowledge of archaic languages
>The rolling of the eyes
>Display of extreme strength and violence and other superhman abilites
Father Gabriele Amorth, one of the most notable exorcists in modern history, relates that many of the truly possessed will become violent if prodded from their hiding place: "During an exorcism I saw a child of 11 held down by four strong men," he relates. "The child threw the men aside with ease. I was [also there] when a boy of 10 lifted a huge, heavy table." As the demon is provoked, it may also react in spurts of aggression by levitating objects or people and hurling them across the room, or by carving words into skin or walls.
>There can be a reaction of the limbs and face—huge physical contortions of the arms, the legs, and the face.
>The demon can speak through the vessel in the voice of the person, saying things that no one might know, using this information to undermine others.
Other than thay symptoms of possession may include tremors and palsy, vocal outbursts, violent headaches, vomiting and stomach cramps and sudden personality changes may often manifest themselves, such as turbulent outbursts. Usually peaceful individuals will sometimes act out by making obscene or lewd comments or threatening others with violence or fear.