Exorcism is an ancient tradition within the Catholic Church going back to biblical times.
While the practice is rare, the Vatican is now sponsoring an exorcism class for priests.
"The request really is coming from the Vatican asking every diocese in the United States to have a trained exorcist," said the Rev. Gary Thomas of the Diocese of San Jose, Calif.
Catholics are not the only ones performing exorcisms today. An estimated 500 non-Catholic Christian groups perform exorcisms in the United States.
In a hotel conference room in Bakersfield, Calif., Bob Larson, who is not a Catholic priest, says he, too, can cast out demons. He and his staff exorcize thousands of people a year, traveling around the world to perform the rituals.
Larson said people were possessed by demons, not the devil himself.
"The devil can't be everywhere," Larson said. "God can be everywhere so the devil has to duplicate the omnipresence of God by sending demons out to do his work."
According to Larson and the hundreds of other Christian deliverance ministers, these evil spirits can cause people to commit horrible acts from small sins to murder.
"More people are possessed today than ever have been in history," Larson said. "We have more permission today to do bad things than ever before. That doesn't explain the mother in Texas who chops off the arms of her baby."
Larson concedes that throughout history people have suffered from mental illness, but he also says that people have always been possessed by demons.
Janelle Mallard was exorcized by Larson. During the ceremony she spoke in a strange voice and flailed around almost uncontrollably.
"I feel refreshed, like something's lifted off my spirit," Mallard said after the exorcism.
"I can't convince anyone this is real except to say look at the newspaper headlines day by day and see if you really think the immensity of the violence and crime are truly the result of just human nature gone mad," Larson said.
Gretchen Passantino is a Christian writer who has studied deliverance ministries. She does not believe Larson is delivering demons.
"What he is doing is exploiting and manipulating people, appealing to their fears, their needs, their sense of inadequacy," Passantino said. "He certainly is a performer. I will leave it to a police department who run fraud units to decide if he is a fraud or not."
Larson spent years working as a radio talk show host and motivational speaker, and he has little formal religious training. Instead, he says his expertise comes from writing books and performing exorcisms at seminars.
The seminars are free, but Larson asks for donations of at least $120 per person to pay for his work and to build a national center for exorcism.
"I can understand people are skeptical," Larson said. "Come and see it. Come and observe it firsthand. Watch it."
ABC's Heather Nauert reported this story for "Good Morning America."