The movie opens up right after the death of Emily Rose, the titular character, most of her story will be shown in flashback during the court questionings of the witnesses involved in the story. The priest, Fr. Moore, is at the house and a medical examiner comes in to give his conclusion of cause of death to the officer. The officer then charges Fr. Moore with negligent homicide. It now must be determined who shall prosecute. The prosecution calculates the prosecutor must be a Christian, preferably a Catholic, and that he must be seen as Church-going and friendly toward the Faith. While this is a calculative decision, it is remarkable as to how in the real world such Satanic thinking operates. We are often presented with a "devoutly Christian" politician presented to us by the media who happens to have firm agreements with the faithlessness of the World because it is only under such an appearance of light that Satan could ever deceive us. How many times have we heard the drivel that Nancy Pelosi or Tim Kaine or Joe Biden are "devout Catholics" while they openly oppose every single Church doctrine?
It so happens that the prosecuting attorney picked is a regular Church-going Methodist. A Protestant. The defense attorney is an agnostic with doubts about her own past. And it is in that remarkable mixture that we are presented with the conversion power of the Church over a heresy. Throughout the course of the trial, we see the defense attorney come under both spiritual attack and receive spiritual protection in her own time of need as she becomes more and more open to the idea that there are spiritual powers that we come into conflict with. The priest, Fr. Moore, is more focused on presenting the Truth of the story of Emily Rose and he does not fear being portrayed as a madman.
Throughout the trial, we see the materialistic side presented by the prosecution to prove the case of negligent homicide. When I consider my old Protestant views and how much of it favored the idea of syncretism of the materialistic viewpoint with Christian theology even when both were incompatible, I see the manifestations of the Enlightenment mindset which Protestantism has given birth to. The "man of faith" is ultimately seen as the faithless and the skeptic. It is he who is exposed as the unbeliever. Whereas the agnostic is shown to have much more faith than she even realizes throughout the movie. It is something that many people don't recognize among our current world how faithless those they present as faithful are. It is the Satanic nature of today's world to present as faithful those who oppose the very Faith that is claimed to represent in an effort to undermine the very essence of the Faith. And that is where the real spiritual battle in the movie lies.
The priest, we find, does not intend to defend his own self. He only intends to present what he believes is the Truth. That is the very Truth of the Victory of Christ. He wants to make it known to the jury, not that he is a martyr, but that Emily Rose is a saint. He does not fight the battle but he puts the battle into the hands of God and the saints and lets them fight the battle. The movie also contains quite a theodicy in it where Emily Rose relates in a note to the priest a brief encounter she experiences with the Virgin Mary prior to her death and how it is in that which she ultimately chose to accept her continued sufferings so that others may come to belief.
The movie is based on the real life exorcism of a German girl named Annelise Michel. Annelise Michel was a college student who went through the exact same struggles as Emily Rose. It was presumed by the Church and the clergy that she was possessed and needed exorcism. The overlap between the spiritual and the material was forgotten and she was ultimately left malnourished and died. The priests involved, and her parents, were convicted of negligent homicide by German authorities. But today, the grave site of Annelise Michel is a place of pilgrimage among many German Catholics who even ask for her intercession as a saint. Through the sufferings of Annelise Michel, many have been brought to Faith. I won't reveal the ending of the trial of Fr. Moore in the movie as that would be a spoiler, but I would strongly recommend it. There are scenes that can be frightening so I would not recommend children see it, the theological message is very important.