Continuity mistake: When William Petersen is talking to his kid in the supermarket, the cereal boxes behind him on the shelves change between two shots. The items behind Kevin also change during the scene. (01:09:05 - 01:10:20)
Factual error: While using the phone in his cell, Dr. Lecktor asks an operator to dial a Maryland area code, but is then connected to the University of Chicago. (00:30:10)
Continuity mistake: When Dollarhyde is shot near the end of the film, he falls on the floor of the kitchen and a pool of blood spreads out from underneath him. In the next shot of his body on the floor, the pool of blood has disappeared.
Continuity mistake: In the scene where Graham uses Freddy Lounds to plant a story about the Tooth Fairy in the Tattler, Lounds places a tape recorder on a desk. A few shots later, the recorder is back in Freddy's hand, and he places it on the desk again.
Continuity mistake: After Will has been to see Lecktor, he is standing near a set of traffic lights with Dennis Farina's character. In the next shot a cigarette mysteriously appears in Will's mouth that wasn't there in the previous shot. (00:21:45)
Factual error: Dr. Lecktor's cell has the hinges on the inside of the cell. They should be on the outside so Lecktor can't compromise them.
Visible crew/equipment: Near the climax, Will Graham is sneaking through the woods, approaching Dollarhyde's house. In one shot, Graham steps more carefully and glances down; the camera is in front of him moving as he's moving. And for a couple of seconds, the camera dolly tracks are visible behind him, just to his left.
Continuity mistake: In the original theatrical version, Graham shoots six rounds at Dollarhyde from a gun that holds five rounds. [In the Director's Cut, one of the shots has been edited out. However, this is still valid for other prints of the film.]
Continuity mistake: When Graham is reviewing the crime scene in Birmingham, his grip on his tape recorder changes. (00:11:30)
Character mistake: In one of the National Tattler headlines, the word "pursues" is misspelled "persues". (00:52:15)
Continuity mistake: When Lektor calls the University of Chicago to get Will Graham's address, the receptionist tells him that it's 3680 Desoto Highway. When Crawford later tells Graham that Lektor released his address to the Tooth Fairy, he says it's 3860 Desoto Highway. (00:32:15 - 01:01:50)
Factual error: When Reba is in the darkroom with Dollarhyde she mentions that he speaks very well but avoids fricatives and sibilants. In linguistics sibilants are a form of fricative and Reba would have known that since she'd obviously studied linguistics. The writers likely meant that he just avoids sibilants (to avoid sounding homosexual) but wanted it to sound more technical. Sibilants in English are the 's' in "see", 'sh' in "shout", 'z' in "zoo", and the 's' in "pleasure". Fricatives would include sibilants as well as the 'f' in "fine", 'v' in "vine", 'th' in "that", and 'th' in "thing" (01:17:30)
Chosen answer: He figured out earlier that the Tooth Fairy drives a van. Graham noticed that at one of the houses, the Tooth Fairy knew everything he had to do and bring with him and at the other house, he didn't know about the new lock on the door. He concludes that this is because the Tooth Fairy got his information from the same home movies that Graham was watching. Once the films were traced to the lab where Dolarhyde worked, it was easy to link them back to him as the only person who'd had access to both families' videos and also drove a van.
Captain Defenestrator