Chantal Hearst spits on the mirror. When we see the mirror again, her spit has disappeared.
Chantal's spit on the interrogation room window disappears in between shots.
There is one scene, a flashback, where it shows Henry jogging around a breakwater, or rock walkway, with the neighbors dog. Here you will see the dog clearly on a leash. This is the only scene where the dog is on a leash otherwise the dog has always been seen running free.
In Puerto Rico, 911 operators answer calls in Spanish, not English.
When Detective Owens goes to get Hearst coffee with milk, he opens the fridge and see milk cartons with "MILK" written on them. Since this is in Puerto Rico, the cartons would have said "LECHE" instead.
After returning from his errand to get Henry a "Cold Drink", it seems detective Owens carries a large Styrofoam cup with a lid attached by pinching the lip at the top of the cup and swinging it as he walks. It would seem to prove that this was a prop - the hollow sound as it hits the table adding to the effect.
In fact, the detective holds a can of soda as well, and he places it behind the cup.
Chantal Hearst's dress varies from having a solid back to being cut out.
In the beginning of the movie at 2:51, the cameraman can be seen in the reflection of the glass on the picture frame to the left of the screen.