When Zack and Bitsey are re-creating Constance's death, you can clearly see Zack bump the tripod-mounted camera as he moves. But in the next shot, the view on the monitor is the same. Such a jolt would have severely changed the composition of the shot.
When Bitsey found the tape in Dusty's house and put it on the VCR we see "Constance" hand-written on the sticker. When she eject the tape from the VCR the sticker had changed it's then machine written or printed.
After Gale puts his son to bed he feeds his fish. Before he feeds them you can see food floating down from a previous take.
When Bitsey Bloom was watching the tape in the motel room before she asks Zack to go re-create the crime scene. A quick short close up of Zack sleeping showed him wearing a watch. Before and after this close up he was not wearing one.
When the kids are playing in the swimming pool full of mud, the sign on the entrance is supposed to be in Spanish, but most of the words are misspelled and no sentences make sense.
When Bitsey enters the prison for the first time, the sign reads in Spanish "Cierre la puerta fuerta." It is misspelled, it should read "fuerte." The word "fuerta" doesn't exist.
To qualify for a death sentence in Texas, the crime of murder on its own isn't sufficient. There needs to be another alongside it, and rape is one. David is convicted of rape and murder and therefore qualifies for the death penalty. But he didn't rape Constance - their sexual encounter was entirely consensual - and medical forensics have, for many years, been able to tell the difference between forced and consensual sex. When Constance's body was examined, they would have concluded that she had not been raped. Therefore David could not be charged with that crime, and he would not have qualified for the death penalty.
When David Gale is reading an email from his wife, the date reads: Tue. Oct. 8, 1994. However, 8 October 1994 was a Saturday.
Huntsville Texas is about four hours away from Austin Texas, yet Bitsy drives back and forth between the two several times during the film and is able to make her 3:00pm meeting time with David in the prison.
Towards the end of the film, Sharon Gale, David's wife, receives the silver suitcase with the post card from Berlin in it. The postcard was mailed from San Francisco to Texas but has no postmark on it in the upper right hand corner as it should.
Constance mentions Illinois' death penalty moratorium, which went into effect in 2000. However, she died in 1994.
At the beginning of the movie when the pickup truck swerves around the girl, the tire squealing sounds like the road surface is asphalt, when it clearly is dirt and gravel.
When Constance is telling David he's on sabbatical, she says, "It was four to two," but her mouth is not moving at all.
Characters complain about the length of the drive to Huntsville, yet drive to Austin without hesitation. From Houston, Huntsville is about an hour's drive away, while Austin is nearly three.
Near the end of the film, when the protesters are outside David Gale's execution, there is a clear shot of a large banner hung across a barricade which reads "Mark 6:10 Murder does not stop Murder." Mark 6:10 actually reads "And He said to them, Wherever you enter a house, stay there until you leave town." (NASB), so the bible quote actually has nothing to do with murder at all.