When Tom Zito bites Al McGrath's ear, he does so from the side, which meant his upper teeth were on the inside of Al's ear. But when the team matches the dental impressions to the bite mark, they match the upper teeth to the outside of the ear.
When looking for the dump site of Hannah, the girl victim, Aiden refers to the "Department of Ecological Protection" -- this does not exist. It is actually the Department of Environmental Protection.
Pete Riggs moves his tongue when Danny inserts the mold to get the impression of his teeth, despite being dead.