The book and film portray the demonic possession of a 12-year-old girl and her exorcism by two Catholic priests. Blatty said he drew inspiration from a 1949 Washington Post story about a Jesuit priest’s successful exorcism of a 14-year-old boy in Mount Ranier, Maryland.

While the U.S. bishops have previously said that the film stands on “shaky ground” theologically, Catholic film critics have said that for the most part, it tries to portray a real exorcism as authentically as possible.

It won two Oscars in 1974 for best sound and best writing and is one of the 20 highest-grossing films of all time. After the film's release, interest in exorcism skyrocketed in pop culture, sparking a subgenre of films surrounding the topics of exorcism and spiritual warfare.  

 

The other film to be shown, The Omen, is a 1976 British-American that tells the story of the son of an American diplomat who is marked with the sign of the Devil and is the Antichrist.

 

In 2006, attempts to film a remake of The Omen were disrupted on location in Croatia, with sets vandalized and burnt down. The producers blamed the Catholic Church for the disruptions, saying they had decried the film and sparked the outrage.

 

Catholic reviews of The Omen tend to urge caution, as the film can be seen as depicting evil in a victorious light.

 

Fr. Cafferty said he hasn’t seen either film, though he is familiar with their controversial content.

 

“They are not the sort of films that I would choose to watch myself. People have told me about the films and I would have seen bits about The Exorcist – I just don't understand why anyone would like to see it in a church,” he said.

 

A spokesperson for the film festival has defended the decision, saying that the abandoned church would enhance the audience's viewing experience, and cited that the church has been defunct for almost 40 years.

“Belfast Film Festival is well known for its site-specific special events,” said the spokesperson told the BBC, citing its 2015 screening of Jaws on Portrush beach as one example.

“The locations chosen add an extra dimension to the screening, and we think the stone cold surroundings of an abandoned church will make for a suitably chilling viewing experience for The Exorcist.”

“Many people will have their own personal reasons for disliking The Exorcist, and we respect their right to that opinion, but the truth is that it was one of the most widely acclaimed films of the 1970s, nominated for 10 Oscars, including Best Picture,” the spokesperson added.

The screenings of The Exorcist and The Omen, to be shown on Aug. 19 and 20 respectively, have already sold out, according to The Times.