It’s a difficult business to pull off a cerebral movie about exorcism–just ask Paul Schrader. In “The Exorcism of Emily Rose” writer-director Scott Derrickson and co-scripter Paul Harris Boardman come closer to the mark than Schrader did with his prequel to William Friedkin’s 1973 classic (retitled “Dominion” for its recent DVD release), but they still don’t hit the target. What they’ve come up with is a curious melange of elements–a picture that’s partly a serious commentary on faith versus reason and state versus church, partly courtroom melodrama, and partly standard-issue horror flick, complete with ghostly images, creaking doors and sudden jolts. It’s not surprising that the components don’t gel.

The plot is based, very loosely, on the notorious case of Anneliese Michel, a German girl who began experiencing the symptoms of what she came to believe was demonic possession in 1968 when she was sixteen, was treated medically without success, waited several years before church authorities agreed to permit an exorcism, and then underwent a long and torturous series of rituals over a period of nearly a year in 1975-76. After she died of pneumonia and malnutrition, the two priests who performed the exorcism, along with the girl’s parents, were tried for negligent homicide and found guilty but sentenced to only six months’ imprisonment and probation following release. Later, the German bishops declared that the girl had not been possessed–medical experts had testified that her condition was due to epilepsy and schizophrenia–but her grave remained a destination for pilgrims who believed that hers had been a heroic struggle against the devil.

Derrickson and Boardman have predictably altered the location of the tale to the United States–presumably an aging East Coast city, though the isolated house of the Rose family appears to be in a desolate area of the Midwest–and the time to the present. But they at least try to maintain the sense of ambiguity that marked the original incident. Their emphasis is on a single priest, Father Richard Moore (Tom Wilkinson), the family’s pastor, who performs the (much-abbreviated) ceremony on distraught college-student Emily (Jennifer Carpenter) after medical treatment seems to have little effect. After Emily dies, the priest (minus the parents) is brought up on charges by D.A. Ethan Thomas (Campbell Scott), a pious church-goer himself but one who believes the ritual a relic of archaic superstition. The diocese uses its usual legal firm headed by smooth operator Karl Gunderson (Colm Feore), who assigns the case to nonbeliever Erin Bruner (Laura Linney), a smart cookie just triumphant in getting an accused serial killer acquitted. The diocese wants the matter settled out of court to avoid any nasty publicity, but Moore insists on going to trial in order that Emily’s story might be told. The script actually offers a double narrative, with flashbacks (usually associated with court testimony) showing the girl’s descent into apparent possession and the grotesque happenings that led to the exorcism alternating with Erin’s direction of the case–an experience that makes the rationalist attorney feel touched by evil forces herself, challenging her agnosticism. She ultimately decides to present a defense arguing, much to the consternation of Gunderson, that demonic possession should not be dismissed out of hand as an explanation, and though bizarre occurrences (like the sudden death of an important surprise witness) nearly derail her chances, the outcome–like the one in real life–tries to have things both ways, although in a more implausible way than the one that occurred in the real case.

The intricate construction represents a interesting attempt to meld together the picture’s various goals, but ultimately the disparate parts war against the whole. On the one hand the picture wants–especially in the material dealing with Emily, played with energy by Carpenter, but also in that related to Erin’s growing unease–to be genuinely scary, employing the usual devices to that end, from gruesome faces appearing on strangers passing the tormented girl on the streets to loud bursts of sound and music (by Christopher Young) whenever doors slam without warning or mysterious forms suddenly spring out of nowhere (or cars screech to a halt before hitting someone). But, as in Schrader’s film, the deployment of such tricks seems rather half-hearted, so that, for instance, when the ultimate depiction of the exorcism–in which it’s revealed that many demons, from Hitler to Satan himself, claim to be inhabiting her body–comes, it’s spookily atmospheric but relatively restrained by today’s standards. (And it’s topped by a strongly spiritual coda which suggests that Emily’s motive in patiently enduring her suffering was a saintly one.) But “The Exorcism of Emily Rose” also wants to be a thought-provoking piece about the battle between faith and reason, so we get a good deal of verbiage that seems a muted version of similarly-themed material in another, though more histrionic, courtroom drama, “Inherit The Wind.” (When the script repeatedly focuses on the notion that the devil’s power to do harm is greatest at 3:00am, which is called the witching hour, one might be prompted to ask a question that Stanley Kramer’s Clarence Darrow surrogate Henry Drummond might have posed: What time zone is that?) And although this more cerebral side of the film is well-cast and acted with quiet authority by Linney, Wilkinson, Scott, Feore, Mary Kay Place (as the judge), Ken Welsh (as one of Emily’s doctors) and Shohreh Aghdashloo (as a defense witness), its grows more wordy and dramatically tepid as the narrative proceeds.

It remains to note that the film is technically proficient, with a properly moody production design by David Brisbin, decent effects by Keith Vanderlaan, and cinematography by Tom Stern that showcases both well. But despite the surface polish, the attempt to meld horror conventions with an elevated debate on the nature of good and evil bears mixed results. There are some good things in “The Exorcism of Emily Rose,” but they don’t add up to a satisfying whole.