When Nick/Johnathan goes up on the charity auction block he announces that he is a man ".....in his thirties". However when Travis presents him with a copy of his driver license it lists his year of birth as 1954, making him 45 in 1999 when this takes place.
When Libby is handcuffed to the car and she accidentally rams the Geo that is in front of Travis's car overboard, the Geo has hubcaps as it's going over, but when the camera cuts to the Geo sinking, the hubcaps have been removed.
Double jeopardy only applies to crimes tried by the same state or the federal government. If a murder occurred in a different state, it is tried independently of what may have occurred in another state. In practice, if it is discovered that the crime for which a person was convicted did not occur, the conviction would be vacated.
In the scene in the Lafayette cemetery, we see that Libby has been put in a mausoleum and then put in a coffin with a body. This is a factual error since burials at the Lafayette cemetery do not involve actually burying people by themselves in a coffin that stays that way forever. The burial process involves putting someone in a very simple wooden box and letting them decompose with other members of family who have been buried before hand. Also the process to open a mausoleum is considerably harder than just opening a door. Bricks and mortar and usually a name plate/stone must be removed to get into a mausoleum. Also under the same line there is not a single mausoleum within the cemetery that would have a window in it. Burials also usually involve the traditional catholic mourning period of 366 days before the mausoleum is opened again, so even if someone had just been recently buried the body that Libby is put next to would not be as un-decomposed as shown in the movie.
When Libby leaves Colorado for New Orleans she travels by plane. As a wanted fugitive air travel would not have been an option open to her as she would have been flagged as wanted and arrested as soon as she tried to fly.
Seattle Police officers are only authorized to wear a turtleneck or tie when wearing a long sleeve uniform shirt (never a white T-shirt). The badge is nowhere close to the actual badge worn by SPD officers. The name tags are black, not silver (almost always cloth sew-on type) and should be worn on the right breast pocket 1/2 inch below the top of the pocket flap.
In the scene when Libby enters the BMW dealership and asks the salesman to run a credit check on Angela Greene, the salesman returns and provides her with a current address. However, in the next scene, when Libby attempts to find Angela in Colorado, a neighbor informs Libby that Angela died three years earlier. Therefore, there would have been no available credit report and current address for a person who had been dead for three years.
As Libby is getting ready to meet Nick to get Matty, she opens the cylinder of the pistol she took from Travis. The close-up of the cylinder shows a round in the cylinder already fired (firing primer dimpled).