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.
When the Lights Went Out
Len and his friend, convince the local priest to perform an exorcism on their house, he refused to do it in the beginning, citing lack of permission from the church and that he will be removed from his priesthood for going against the order of the church. Len and his friend then blackmail the priest into performing the exorcism by showing him photos of the priest engaging in illicit affair with his housekeeper. Len threatened the priest that they will release the photos into public if he refused to help the family. The release of photos would have lead to the priest's dismissal. The priest then agrees to do the exorcism and takes them to the church to prepare the articles he needed to do the exorcism. The priest told them that the monk while he was alive, preyed on the young uneducated girls in the neighbourhood and cut off their tongue so that they could not expose him. He killed the young girl as she was educated and could have exposed his deeds by writing about it. After the incident the monk was secretly tried and hanged and buried in secrecy in order to save the honour of the church. After hearing the story from the priest, the three of them proceed to his house, where they start chanting biblical quotes. The spirit, protests their chantings by throwing household items on the trio. After some efforts the priest manages to drive the spirit out of their house.