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.
The Devils (film)
Laubardemont summons the lunatic inquisitor Father Pierre Barre, a "professional witch-hunter," whose interrogations actually involve depraved acts of "exorcism", including the forced administration of enemas to his victims. Sister Jeanne claims that Grandier has bewitched her, and the other nuns do the same. A public exorcism erupts in the town, in which the nuns remove their clothes and enter a state of "religious" frenzy. Duke Henri de Condé (actually King Louis in disguise) arrives, claiming to be carrying a holy relic which can exorcise the "devils" possessing the nuns. Father Barre then proceeds to use the relic in "exorcising" the nuns, who then appear as though they have been cured – until Condé/Louis reveals the case allegedly containing the relic to be empty. Despite this, both the possessions and the exorcisms continue unabated, eventually descending into a massive orgy in the church in which the disrobed nuns remove the crucifix from above the high altar and sexually assault it.