When Maria is thrown off the table during her exorcism, one of cameras shows her heart monitor with her vitals flashing. They should not be reading anything as the throw would have disconnected the wires.
When the film begins with the 911 recording the date is stated to have been October 30, 1989. However, when the police chief is talking on the news later he states that dispatch received a call late the night of October 20th.
During the first visit to Maria from Isabella and Michael, Michael's camera seems to be beside Isabella but the upper camera is not showing anyone beside her.
When footage of Maria Rossi is shown being declared as insane, it's actually real footage of the murderer Aileen Wuornos - you can see her talking to her lawyer at the end of the clip.
When the characters speak Italian they all do so with heavy American accents. The list includes: (1) Guard at the Centrino Assylum (2) Possessed girl on the Vatican tape (3) Police officers who go into Ben's and Michael's apartment
(around 16:58) In the first hospital scenes, which were set in Italy but filmed in Romania, the sign above Dr. Costa's office says "Doctor Costa". The spelling for the title 'doctor', in Italian, is 'dottore' (abbreviated, Dott.). The spelling for the same title in Romanian is 'doctor'.
When boarding and disembarking the flight to Rome the interior is clearly that of a single-aisle narrow-body regional airliner. It ought to have been a wide-body twin-aisle transatlantic aircraft.
The interior of the plane traveling to Rome is that of a TAROM Romanian Air Transport aircraft. Logos of the airline are visible on headrest covers and the overhead exit sign is in Romanian. The movie was shot in Romania.
During the 1989 flashback, the CSI agent is using a BIC ultra round stic grip pen to point out features in the crime scene - a ballpoint pen that would not be created for over a decade.
When Isabella meets her mother the first time in her cell, a crew member is reflected in the window behind Maria.