Exorcism
In Catholic Christianity, exorcisms are performed in the name of Jesus Christ. A distinction is made between a formal exorcism, which can only be conducted by a priest during a baptism or with the permission of a bishop, and "prayers of deliverance" which can be said by anyone.
The Catholic rite for a formal exorcism, called a "Major Exorcism", is given in Section 11 of the Rituale Romanum. The Ritual lists guidelines for conducting an exorcism, and for determining when a formal exorcism is required. Priests are instructed to carefully determine that the nature of the affliction is not actually a psychological or physical illness before proceeding.
Exorcist II: The Heretic
Father Lamont visits the institute, but his attempts to question Regan about the circumstances of Father Merrin's death are rebuffed by Dr. Tuskin, who believes that Lamont's approach would do Regan more harm than good. In an attempt to plumb her memories of the exorcism, and specifically the circumstances in which Merrin died, Dr. Tuskin hypnotizes the girl, to whom she is linked by a "synchronizer", a revolutionary biofeedback device used by two people to synchronize their brainwaves. After a guided tour by Sharon of the Georgetown house where the exorcism took place, Lamont returns to be coupled with Regan by the synchronizer. The priest is spirited to the past by Pazuzu to observe Father Merrin exorcising a young boy, Kokumo, in Africa. Learning that the boy developed special powers to fight Pazuzu, who appears as a swarm of locusts, Lamont journeys to Africa, defying his superior, to seek help from the adult Kokumo.