Character mistake: In the initial meeting at FBI headquarters, the agents mention the Zodiac killer. Gideon says about him "Yeah, and he killed for 30 years without being caught." In actuality, the Zodiac's known victims were killed between 1966 and 1970. In letters to the public, Zodiac claimed responsibility for several other murders (most of which were solved without being attributed to Zodiac), but no later than 1974. Gideon's statement was off by at least 22 years.
Factual error: The train car in which Elle and the other passengers are held hostage is supposed to be an Amtrak type long distance railroad car traveling from El Paso to Dallas, yet on the inside of the car we can see a large poster showing the Washington, DC Metro system map.
Factual error: In this episode Gideon mentions Andrei Chikatilo, and says that he lived in Ukraine (and that this is why he remained uncaught for so long). While Chikatilo was born in Ukraine, he lived in Russia for most of his life, and all of his murders happened here. An expert like Gideon should not make this kind of mistake.
Continuity mistake: When Reid and Lila are in the pool, kissing, he explains how it is wrong that they are out in the open, and in a pool. Lila then kisses him again, and the paparazzo in the bushes takes pictures. In the first shot of this kiss, a close-up of Reid and Lila, her arms are down by her sides, but when seen through the camera, her arms are suddenly around his neck. Back to a close-up, and her arms are once again down in the water.
Continuity mistake: At the end when the FBI is going to the apartment where the killer is holding the hostages, Gideon puts on a bulletproof vest while standing next to the car talking to the cop and a second later while he's walking toward the building he puts the vest on again.
Continuity mistake: In the scene when the investigators at the police station realize who the killer is, the deputy enters and says that a revolver is missing. However, when Cory pulls out the weapon in the woods, he is holding a semi-automatic pistol. The deputy would know the difference between the two, but still uses the wrong term (a revolver may be referred to as a pistol, but an automatic like Cory had stolen can never be called a "revolver", as the chamber does not revolve).
Continuity mistake: In the scene just after Gideon talks to Cherish's mother we see him start to walk toward the rest of the team. In the wide shot we see Reid standing with his hands in his pockets and jacket open, we then see him close his jacket and cross his arms as Gideon gets closer, but in the very next shot (the close up on Reid) we see his jacket open and his arms at his side once more.
Character mistake: Morgan asks Reid what track on the CD (Some Kind of Monster by Metallica) would help an insomniac sleep. Reid replies with "Enter Sandman" however, Some Kind of Monster doesn't feature the song Enter Sandman.
Other mistake: Just after they were finished explaining that you can not tilt the mystery package because it would instantly blow up, they show the little girl at her doorstep holding the package completely tilted. Just when you think that means that this package now doesn't fall into the "explosive" category, they then show the mom freaking out, and later police making the girl hold the package in a completely different (non-tilted) position.
Continuity mistake: In the elderly victim's home, when Gideon is going through the dresser drawers he finds the small frame with the picture of her son, and there is a blue frame lying in the drawer, but in the next shot that blue frame is lying on the dresser even though he never touched it.
Add timeSuper Grover
Revealing mistake: When Hotch and Spencer are interrogating Eddie, Spencer shows him the three photos of the people he has killed. Eddie makes a gesture as if to speak and points at Spencer, at which point we see a shot of Spencer and he very obviously glances into the camera.
Continuity mistake: Before the BAU catches the serial killer Carl Arnold, they used a heat sensor and it shows five people sitting at a table. They said there were three adults and two kids, but when they break in the house, the mother and one kid were sitting at the table, the father was tied up nearby, and Carl Arnold and the other child were in the basement. They were found by Derek Morgan right before Carl Arnold threw the child at Gideon, who fortunately caught him.
Continuity mistake: At the start we see Spencer explaining to Gideon about the Boston Strangler, his orange shirt is untucked at the front with both sides of his shirt being visible. Camera shows Gideon walking off and now only 1 side of his shirt is untucked.
Continuity mistake: They keep showing the aerial view of one type of jet (such as Gulfstream 100 with its rectangular windows), but the inside shots are always in a "heavy" Gulfstream (such as Gulfstream IV or Gulfstream V, which have round windows). Also, the tail numbers (the N-numbers written on the engine) are always different in the aerial views. Some end with GV, some with SP etc.
Factual error: In the episode, the case is handled locally by the Wilmington Police Department. In reality, Wilmington Police only operate within city limits. Based on the suburban locations pictured, this case would more likely be handled by Delaware State Police or New Castle County Police.