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.
Exorcism of Roland Doe
According to author Thomas B. Allen, Jesuit priest Father Walter H. Halloran was one of the last surviving eyewitnesses of the events and participated in the exorcism. Allen wrote that a diary kept by attending priest Father Raymond Bishop detailed the exorcism performed on the pseudonymously identified "Roland Doe" aka "Robbie". Speaking in 2013, Allen "emphasized that definitive proof that the boy known only as ‘Robbie’ was possessed by malevolent spirits is unattainable. Maybe he instead suffered from mental illness or sexual abuse—or fabricated the entire experience." According to Allen, Halloran also "expressed his skepticism about potential paranormal events before his death." When asked in an interview to make a statement on whether the boy had been possessed, Halloran responded saying "No, I can’t go on record. I never made an absolute statement about the things because I didn’t feel I was qualified."