Every culture has an understanding of demonic possession, Father Fortea said. "But they don't have a solution for it. Jesus brought the solution. Jesus taught us to do exorcisms.

"Exorcism is a sign of the power of Jesus that the power of the kingdom of heaven is here on earth," he added. "Every exorcism is a gift that helps us believe."

The need to expel demonic spirits from a person's body is neither common nor rare, Father Fortea said.

When his bishop first called on him to study exorcism in the late 1990s, Father Fortea said he thought exorcism was a rare event that might occur once or twice in a century.

But when more and more people came to him for help, he realized demonic influences were much more active, especially in those who associated with witchcraft, magic, Santeria and some New Age practices.

Unlike the movies, most possessed people seem perfectly normal, he said. The signs are usually subtle -- trembling or spitting.

The church has specific prayers and rituals for conducting an exorcism, he said. But when he is training priests, he tells them not to worry about technique. "I tell them to surround the demoniac with the glory of God," he said. "Center on God."

Father Fortea cautions people about seeing the devil everywhere.

For instance, some people worry about letting their children anywhere near "Harry Potter" books and movies.

Father Fortea said he thinks "Harry Potter" is great fun as long as it is regarded as entertainment.

"I looked a lot like Harry Potter when I was a boy," said Father Fortea, who has seen one of the films. "When Harry went to Hogwarts, it made me remember when I went to seminary."

He cautioned parents about forbidding things to their children. "Prohibition has to be used carefully," he said. "People think we are more protected by forbidding things. If you forbid Harry Potter, why not Tolkien?"

Demonic spirits take over the body, not the soul, he said, which is why the sacrament of confession is more important for the average Catholic than exorcism.

But he said anyone can be approached by evil spirits, even Jesus.

He urged people to use moderation and common sense and to build up their faith with the sacraments and devotional practices of the church.

"A lot of temptation isn't from the devil. It's from the individual," he said. "In fact, 98 percent of temptation comes from our heart or the world. You can avoid sin because God is willing to give us grace."

And if they feel the need to consult an exorcist, they should call their bishop. Only certain priests have the training and the permission to conduct exorcisms and the list is not made public.

Father Fortea, a priest and theologian specializing in demonology, studied and graduated from the University of Navarre with a degree in history. In 1998, he wrote his thesis on "The Exorcism in Modern Times" and defended it before the secretary of the Commission for the Doctrine of the Faith of the Spanish bishops' conference.