Scott Derrickson does many things right in this little "courtroom horror" picture. His possession scenes are top notch, with most of the chills coming from jarring camera work and generally only subtle special effects. Rarely is a special effect in this film more than a digitally altered scary face or subtly enhanced human ability (as often seen in The X-Files). The rest is done through editing, lighting, and scoring. I believe that Derrickson did this for a very specific reason - to add credibility to both sides of the courtroom argument. Was Emily possessed by demons or mentally/physically ill? Emily's feats of strength, obscene bodily contortions, and other frightening abilities can all be explained by both science and religion. For some of the more supernatural moments that Emily experiences, Derrickson lets us observe from two perspectives: demonic influence and objective science. Since this is of course a horror picture, there are noticeably more scenes of the former. This is a good thing because Derrickson unfortunately does not handle drama very consistently in this picture. Several key moments in the film, including a fervent assertion made by the district attorney, that should have resonated with the audience instead made everyone in the theater laugh at the scene's ridiculousness. Still, the scares are top notch (particularly a long exorcism scene which begins like Friedkin's Exorcist but then takes some surprisingly different turns) and presenting both religious and scientific explanations for the possessions (which was never an option for the head-spinning, levitating Reagan) will satisfy both believers and skeptics. Worth seeing.