When Erin turns her alarm clock around the first time her hairstyle and color are completely different.
The prosecutor is only partially correct in that humans have two sets of vocal cords (they are properly known as vocal "folds"). He calls them "duel sets," consisting of the "superior vocal cords" and the "primary ones." They are correctly known colloquially as "true vocal folds" and "false vocal folds." The FVF are called "false" because they are made up of membrane, whereas the true folds have a deep layer of muscle tissue and can be controlled. The FVF can be recruited by powerful airflow and/or by disciplined muscular movements by the muscles surrounding them. However, they cannot be "activated" in the sense that a muscle can, and would not produce a different "voice." At most, some harmonic overtones or vibratory interference (such as that heard in Tibetan chanting) might be heard. The prosecutor uses the term "dual voices" as if it means two separate actual voices, as if "voice" was being produced by two distinct sets of vocal folds, which is not possible in humans. The writers confused it with some individuals' ability to produce two different fundamental frequencies by vibrating each of the true vocal folds at different rates, but the act of forming words is not determined at the vocal fold level, but by resonances created by the positions of the articulators in the vocal tract.
After the verdict has been announced, and the judge has issued the date for sentencing, the defense attorney requests the judge and jury pass sentence immediately and the judge and jury comply and the defendant is allowed to walk free having been credited for time served. This would never happen in reality, the judge would dismiss the motion and the jury having been discharged would have no authority to recommend sentence.
When Erin Bruner meets with Father Moore in jail, the whole cell block is dark and barely lit. And being a lawyer, Erin meets with Father Moore in his jail cell without the presence of guards or police. This is not done for the explicit safety of both the prisoners and those that visit them.
The stop button is pushed on the tape recorder during the courtroom scene, but the tape continues to play for a few more seconds.
When Erin Bruner is awakened at 3 am by the exorcism tape playing, she goes to push stop. But when the tape player is actually seen, the reels are not turning, therefore when she presses the stop button, the reels remain unchanged.
When Father Moore recites the Lord's Prayer he incorrectly quotes a line as "Thy will be done on earth, as it is in heavenly", so substituting "heavenly" for the correct word "heaven". "Heavenly" is nonsensical in context and not an error a priest would make.