There aren't many people more disturbed or twisted than Eli Roth - the guy who gave the world Cabin Fever and both Hostel films. His latest creation, The Last Exorcism, is his own response to both the handheld craze of Paranormal Activity and the long-lasting reputation of The Exorcist. Which he first saw when he was six - something that might explain quite a lot.

In the run-up to The Last Exorcism's UK release, we sat down with Eli Roth (producer) and director Daniel Stamm to ask them about making a modern movie about possession. The resulting discussion covered everything from religious fundamentalism and District 9 to bashing cats to death with video cameras...

After the opening weekend in the US, how are you finding the success of The Last Exorcism?

ER It’s great to have got the number one spot – it feels amazing. It’s been a really difficult summer: the week before there were things like The Expendables, whereas we made a movie for $3 million that took over $20m. People just went crazy for it.

DS It’s crazy. The last movie I made cost $3,000 so anything above that is great! Seeing posters everywhere with my name on it is weird.

How did the project come about?

ER I liked the script when I first saw it. I obviously am a huge fan of The Exorcist and the subject of possession – it’s in all my films, from Cabin Fever, which is about a disease taking over your body, to the Hostel movies, which is more about someone else taking control of your body. I saw The Exorcist when I was six years old and it fucking traumatised me! I would go to bed worrying about being possessed, and my parents would be like "don’t worry, we’re Jewish, we don’t believe in possession". I was convinced I would be the first example of Jewish possession. A lot of people would argue that did indeed happen… But yeah, we felt it was time for another possession story where the characters are aware of The Exorcist and actually acknowledge it. You can never make a film scarier than The Exorcist, but that doesn’t mean you can’t tell a great story about the same subject matter. 

Keeping the documentary approach throughout the film dictates the style of the film, but you did include things like an orchestral score. How did you balance the realism with other cinematic conventions?

DS We actually decided to have a score very early on, because it kept that emotional experience of the movie. We were always deciding how fanatical to be about the documentary style; if people were shooting with a camera and saw a demon, they wouldn’t go for a reaction shot from Reverend Cotton Marcus, they would stay on the damned demon! But in editing, the emotions of the protagonist were missing, so we went back and shot Cotton’s responses. It was more important in the end to keep the audience emotionally involved.

ER District 9 started as a documentary and then switched into a normal narrative and you don’t really even think about it – because you’re caught up in the story emotionally. For us, it’s about Cotton’s journey. He starts off in control but gradually loses it, and Daniel does this amazing job of showing this slow descent into hell. 

Dealing with such an extreme religious topic as possession, how realistic did you strive to be about backwater American fundamentalism?

ER Well, 42% of Americans believe in God and a lot of people believe in pure creationism. It was important in the writing to get the facts right – for example, the exorcism academy from the Vatican that we mention is actually true. That story came out in 2009 while we were developing the movie. It was important for us that we showed both sides; a devout religious man who falls for Cotton’s fake tricks, but also a father who simply loves his daughter.

DS Every religion has its own form of exorcism – that’s across the world, not just in America. We even had our own exorcist on set, who was the brother of one of our drivers. We were just driving along and he said “oh yeah, my brother is an exorcist” so we stopped the car and picked him up! He was very matter-of-fact about it, that it was just his job, like he worked in Virgin Megastore or something!

What made Patrick Fabian the perfect exorcist for the film?

DS When I do casting, I like to sit in the waiting room and pretend to be one of the actors. I get to talk to them when they’re tense and nervous – you really learn something. For Patrick's audition, I was asking actors to improvise a sermon, so he came in with this 8 minute sermon. I asked him to do something that would take half the time, but instead of shortening it or taking bits out, he just spoke twice as fast! There was this energy he had that made you want to stand up and shout about whatever it was he just said – which is where the idea of the banana bread sermon came in.

Killing animals on screen is not cool - especially cats. How do you feel about that?

DS I have a cat at home and the creepy thing was that my cat looked exactly like the cat in the movie – they brought it into the room, it was white, had two different coloured eyes, and it was actually called Daniel. I thought the universe was trying to tell me something, then decided to go ahead and smash it up anyway.

ER I actually do a lot work with the PETA (People for the Ethical Treatment of Animals) – I recently shot an anti-violence film for them – so I figure, well, they kind of owe me a cat. That Public Service Announcement I did probably meant I saved the lives of a lot of animals, so I’m allowed this one!

Without wanting to spoil it, a quick word on the ending. It's unexpected, ambiguous - it's divided a lot of people. What reaction were you aiming for?

DS What was important to me was that we weren’t making a movie that solved the question of there being a God. We wanted to show both sides of science and religion and not see the definitive outcome of Cotton’s battle with his own faith.

ER It’s part of the fun of making a movie so cheap – when you’re making something for $80m, pretty much your average budget, it gets watered down through focus groups and market testing. People are used to everything being solved, so it was fun to see people come out of the movie so fucked up! People either got it or were kind of angry. I love movies where you leave and spend hours arguing or discussing the ending. For me, the movie is a continual test of Cotton’s faith – he says himself if you believe in God, you have to believe in the Devil, but he doesn’t actually believe. He just thinks everyone else around him is crazy and that he knows better.

The Last Exorcism is released in UK cinemas on Friday 3rd September. You check out the trailer over here, or read our review.