Emily Rose, a 19-year old American teenager, dies of self-inflicted wounds and malnutrition following an attempted exorcism. Father Richard Moore, the Catholic diocesan priest who attempted the exorcism is arrested and sent to court. While the archdiocese want Moore to plead guilty to minimize the crime’s public attention, Moore instead plans to plead Not Guilty. Erin Bruner, an ambitious lawyer hoping to use the trial to become a senior partner in her law firm, takes on the case. Moore agrees to let her defend him if he can tell the truth behind Emily’s story.
During the trial, Emily’s past is told through flashbacks and the evidence provided by witnesses. The trial’s prosecutor is Ethan Thomas, with Judge Brewster presiding. The prosecution claims Emily suffered from epilepsy and psychosis to explain her behaviour. Emily receives a scholarship to study for a bachelor’s degree, but shortly displayed sights of demonic possession after she began attending classes, experiencing visions and physical contortions. Diagnosed with epilepsy, Emily receives anti-seizure medication but the treatment fails to cure her. A friend named Jason took Emily back home to her family, where she continued displaying traits of possession until Moore was summoned to attempt an exorcism.
Bruner begins experiencing supernatural phenomena at home, waking up at 3:00 a.m. to the scene of burning material. Moore warns her she may be a target for the demons, revealing he too has experienced similar phenomena on the night he was preparing the exorcism. With the prosecution building a strong case, Bruner steps up her own by trying to legitimise Emily’s possession. She summons anthropologist, Sandira Adani, to testify about the beliefs about spiritual possession from various cultures, but Thomas dismisses her claims as nonsense. Graham Cartwright, a medical doctor who attended the exorcism, gives Bruner a cassette tape on which the exorcism was recorded.
Moore is called to the stand where he plays the tape. As seen through a flashback, Moore, Emily’s father, Jason, and Dr. Cartwright participate in the exorcism while her mother and sisters pray in the living room. During the Lord's Prayer, Emily attacks, causing the family cats to become agitated by demonic presence and attack Moore. As Jason and Cartwright help Moore, Emily escapes her restraints, leaps out of a window, and flees to the family barn. The others give chase, Moore continuing the exorcism and demanding to know the demon’s name. It responds by revealing there are six demons – those who possessed Cain, Nero, and Judas Iscariot, a member of Legion, Belial, and Lucifer himself. The exorcism abruptly ends with Emily fainting, and runaway horses injuring those present. Thomas reasons that Emily’s behaviour can be explained by learning ancient languages at school and her epilepsy.
Moore then reads a letter left by Emily the day before she died. A flashback reveals the day after the exorcism, Emily is visited by the Virgin Mary in a field near her house. Offered a choice between ascending to Heaven or remaining to become a martyr but prove the existence of God and demons, Emily chooses the latter. Moore explains she then received stigmata on her arms, but Thomas claims she gained the markings from grabbing a barbed wire fence.
The jury ultimately reach a verdict of guilty, but ask Brewster to give a sentence of time served, to which she agrees. Bruner is offered the position she wanted, but declines and resigns. Bruner and Father Moore visit Emily’s grave, where Moore believes that, in time, Emily will be regarded as a saint.
The screenplay was written by director Scott Derrickson and Paul Harris Boardman; in honor of the contributions of Boardman and other collaborators on the film, Derrickson chose to forgo the traditional "film by" credit. According to Derrickson's DVD commentary, he chose Boardman as his co-writer because Derrickson sees himself as a believer and Boardman as a skeptic, and believed the pairing would provide the screenplay with two different perspectives, thus providing the film some ambiguity as to whether it supports a religious/supernatural interpretation of the events depicted, or a more secular/medical interpretation.
The character of Emily Rose was inspired by the story of Anneliese Michel. The film is based on Felicitas Goodman's book The Exorcism of Anneliese Michel. German director Hans-Christian Schmid made his own film of Michel's story, Requiem, around the same time in late 2006.
As of April 2012, The Exorcism of Emily Rose had made $144,216,468 worldwide. In 2006, the Chicago Film Critics Association listed the film in their Top 100 Scariest Films Ever Made at #86. Jennifer Carpenter, whose "demonic" bodily contortions were often achieved without the aid of visual effects, won "Best Frightened Performance" at the MTV Movie Awards in 2006; however, according to review aggregator Rotten Tomatoes, critical reception to the film was overall mixed. As emphasized by Roger Ebert, who described The Exorcism of Emily Rose as "intriguing and perplexing", the film "asks a secular institution, the court, to decide a question that hinges on matters the court cannot have an opinion on". Ebert noted that "the screenplay is intelligent and open to occasional refreshing wit". Paul Arendt from BBC outlined that "the flashback story... is high-octane schlock that occasionally works your nerves, thanks to a committed performance from Jennifer Carpenter".
The general consensus between 150 critics was that "[the film] mixes compelling courtroom drama with generally gore-free scares in a ho-hum take on demonic cinema." It holds a 45% 'rotten' approval rating on Rotten Tomatoes, based on 150 reviews. On Metacritic, it has an overall score of 46 out of 100, based on 32 reviews.