Scerbo doubts Mother Teresa was the victim of full-fledged demonic possession and in need of an exorcism.
In contrast to Roman Catholic ritual, many protestant exorcisms are straightforward and may not appear much different from a normal prayer service.
"We would not see it as any elaborate ritual," says the Rev. J.R. Hall, editor of the Pentecostal Herald and member of the United Pentecostal Church. He says an exorcism might involve nothing more than prayer and laying hands on the afflicted.
Many conservative protestants see the devil as an active force in the everyday lives of people, and feel that exorcism is the natural way to deal with it. They might undergo several exorcisms — also called a "deliverance" — a month.
New Age religions also have their own brand of exorcism, believing that spirits of the dead and other supernatural creatures routinely interfere with and sometimes possess the living, and must be told to leave.
Possession vs. Mental Illness: How Can You Tell?
Like many protestant groups, United Pentecostal Church members believe the Holy Spirit gives them the power of "divination" — to sense when a demon is afflicting someone.
Many people might be violent, depressed, or irreligious without any supernatural involvement.
"Through the Holy Spirit, you can tell it's more," says Hall of genuine cases of possession.
Pastor Steven Waterhouse, an evangelical Christian who heads the Westcliff Bible Church in Amarillo, Texas, has written about the differences between mental illness and possession.
"I think there are such things as demon influence but I think it's rare," he says.
"People are too quick to diagnose demons. Human nature is plenty evil on its own."
Amateur Exorcisms Linked to Deaths
Exorcism has caused a number of real-world tragedies over the years, including several deaths.
Pentecostal ministers in San Francisco pummeled a woman to death in 1995, as they tried to drive out her demons.
In 1997, a Korean Christian woman was stomped to death in Glendale, Calif., and in the Bronx section of New York City, a 5-year-old girl died after being forced to swallow a mixture containing ammonia and vinegar and having her mouth taped shut.
In 1998, a 17-year-old girl in Sayville, N.Y., was suffocated by her mother with a plastic bag, in an effort to destroy a demon inside her.
Cuneo reports that a Wisconsin woman successfully sued her psychiatrist in 1997, after he diagnosed her as diabolically possessed, and having 126 personalities, including the bride of Satan and a duck. The experience left her suicidal, she claimed.
Overall, many involved in exorcism say the prayers and rituals involved are safe and may offer some comfort to true believers who are not actually afflicted by demons.
"If it's real to the person, you have to take it seriously," says Eddie Gibbs, an Anglican priest and professor at the Fuller Theological Seminary in Pasadena, Calif. "I do believe that there is an intelligence behind evil," he insists.
But, he cautions: "We mustn't be gullible."