New York ? While doing research for a big-budget action movie, filmmaking duo Scott Derrickson and Paul Harris Boardman began working with a New York City police officer whose area of expertise was investigating paranormal phenomena.

The officer introduced the pair to unusual evidence he had collected through the years.

“He gave us a bunch of tapes and a bunch of videotapes of eight or nine exorcisms,” writer-director Derrickson recalls. “There was something about those materials that was frightening to me in a way that I’d never been frightened before.”

Among the items was a recording of an actual exorcism conducted in the 1970s on Anneliese Michel, a German college student who claimed to endure the torments of demonic possession.

“The basic true story was that there was a girl who was recognized by the Catholic Church as being possessed,” explains Derrickson, who was interviewed along with the cast during roundtable sessions in Manhattan. “They authorized her exorcism. And after a series of them, the girl died and the priests who performed the exorcisms were subsequently arrested and tried for negligent homicide.”

Jennifer carpenter stars as the tormented titular character in The

Derrickson and Boardman knew they had stumbled upon their next picture.

With “The Exorcism of Emily Rose,” which opens nationwide today, the pair have used the case as a springboard for a fictional flick that combines horror and courtroom drama in a unique hybrid.

“I didn’t know if it was going to work,” says actress Laura Linney, who headlines as the lawyer saddled with defending the priest (Tom Wilkinson). “How do you combine the tension of a courtroom drama and the fear of a supernatural horror film? How do those things fit together? Can they fit together? Does the tension of one and the fear of the other work together, or do they cancel each other out?”

Among the other challenges was the baggage that went along with using the word “exorcism” in the title. It immediately ensured the piece would be compared to the Oscar-winning “The Exorcist,” the granddaddy of all scary movies.

“It’s my favorite horror film,” Derrickson says of the veteran film. “In the writing of it, we were aware we were going to have to take a different approach from that movie. The fact it’s a courtroom movie solves a lot of it because it’s immediately a different kind of vellum than that.

“But there’s that burden you carry of the original ‘Exorcist.’ How do you make a movie like this and not try and out exorcise ‘The Exorcist?’ How do you not out-shock value, out-gore and out-disgust the audience?”

Discovering Emily

The project obviously inspired a lot of questions from the filmmakers and actors. But the answer seemed to lie in the casting of Jennifer Carpenter as Emily Rose.

Prior to that, the all-but-unknown performer’s biggest screen credit was as a snooty rival in the comedy “White Chicks.” But Linney had shared the stage with Carpenter in a recent Broadway production of “The Crucible,” and she recommended the newcomer to the director.

“When Jennifer did her audition, she gave me the same feeling that I had when I saw those videotapes of those real exorcisms,” Derrickson relates. “It felt very alien-like. It gave you this feeling of, ‘This doesn’t feel like human behavior.’ That’s a very hard thing for an actress to do.”

• Audio interviews with Jennifer Carpenter and Laura Linney
• Jennifer Carpenter: Was there any trickery to help you achieve the “possessed” voice?
• Laura Linney: Did you do any research into the rite of exorcism
• The supernatural goes on trial in ‘Emily Rose’ (09-09-05)

The 25-year-old Juilliard graduate had never seen “The Exorcist,” and she avoided the urge to screen it. Instead, she waded through tapes of epileptics and their seizures.

“I watched a rough cut (of ‘Emily Rose’) not long ago and saw my body bend in all kinds of ways and thought, ‘I didn’t know I could do that,’ Carpenter says. “I think a lot of the times I was just running on adrenaline.”

Derrickson adds, “In directing the movie, I took even more of the visual effects and makeup effects out of it, primarily because of Jennifer Carpenter. She was so terrifying all by herself that this desire we had to make a realistic movie just took on a whole new level of potential.”

True believers

Now that “The Exorcism of Emily Rose” is hitting theaters, Derrickson and Boardman are coming to grips with their own beliefs in the supernatural.

Writer-producer Paul Harris Boardman, left, and writer-director Scott Derrickson survey a scene on the set of their horror-drama The

“We have a little bit of a Scully/Mulder approach, where one’s more of a skeptic and one’s more of a believer,” says writer-producer Boardman, who adopts the cynic’s stance in “The X-Files” analogy.

“Has it made me a believer in demons? No. But the evidence is just too strong to dismiss it out of hand and be cavalier about it and deprecate people who think that.”

On the other side of the theological fence is Derrickson, a self-described “recovering fundamentalist.”

“I definitely am a believer,” he says. “I believe in demonic possession. I believe in this phenomenon. I believe in the spiritual realm.”

Did the experience of making the film reinforce those values?

Derrickson responds, “I think listening to those (exorcism) tapes took care of that.”