The Rite is notable in its portrayal of a teenage girl whom seasoned exorcist Fr. Lucas describes as demonically possessed, but whom doubting seminarian Michael Kovack sees as a “sick girl” who “needs medication” when, having expressed doubt about the whole concept of demonic possession in the exorcists’ class he is taking in Rome, he is referred to Fr. Lucas by his instructor at the Vatican training course for future exorcists, and invited to observe this particular exorcism.
During the course of the class, Kovack had expressed “reasonable doubt” that persons thought to be possessed, having been described by the instructor as “having periods of lucidity” and reletive normal behavior, could be suffering mental illness, because “paranoid schizophrenics have periods of lucidity, too”.
While taking the course, Kovack meets a female reporter who is also following the course as a means of gathering background information on the subject of Church policy and belief on the subject of demonic possession, and what motivates and drives a man who becomes a priest-exorcist in this day and age. To that end, she follows him as he participates in the course, and his involvement with an individual exorcism and his relationship with Fr. Lucas grows. She has a personal interest in the question of whether certain individuals are “possessed” or “mentally ill”, and how to tell one from the other, because, as she later reveals to Kovack, she has a brother who had been diagnosed as mentally ill who now lives in an institution.
Kovack discovered that the girl was a victim/survivor of incest (her father is responsible for her pregnancy, the reason she is not taking medication) and the girl, impregnated under circumstances, he presumed “clearly didn’t want her baby”, leading to his speculation that with the purpose of harming the fetus inside her, she had swallowed the large, old-fashioned nails she is seen to cough up following the exorcism. However, unlike most mentally ill persons who engage in self-harm, it is made clear that she knows things about Kovack that she could only have gained knowledge of telepathically, which initially seems lost on Kovack, though she refers to specific items and incidents in his life which she could not have possibly known about upon meeting him for the first time and having no knowledge of his background.
When they discuss her case after the exorcism session, Fr. Lucas acknowledges that mental illness may well be part of the picture, but although he claims that he _is_ (also) a doctor (details are not given, nor is his status as such verified in the picture), he refrains from characterizing mental illness as her primary diagnosis or as an alternate explanation for her symptoms, which in his role as a Catholic priest, he characterizes as typical of demonic possession, a separate and distinct phenomena in its own right.
When the girl gets worse instead of better, she is taken to a hospital (presumably a conventional hospital, rather than a “State Hospital”) where she is characterized as mentally ill, and thus given medication and put in 4-point restraints. (Whether the old enameled iron bedstead and cavernous Renaissance-looking building, coupled with modern patient-monitoring equipment is a realistic portrayal of a hospital in Rome, is another story.)
In yet another mystery that keeps the element of reasonable doubt in her case, she nevertheless manages to suffer sudden “massive internal hemorrhaging” causing both herself and the baby to die, though she had remained physically chained to the hospital bed.