Criminal Minds (2005) - 4 mistakes in whole show

Character mistake: In season 4, episode 9 "52 Pickup", in the scene where Jordan is describing the case, the writers made a large error concerning the M.O. of the UnSub. Agent Jordan states that the UnSub makes his victims clean up their own murders, and they arranged the cleaning supplies in a triangular pattern. The cleaning supplies were bleach, ammonia and garbage bags. This would be excusable if she hadn't also added that both bleach and ammonia were found under the victim's fingernails. If you mix ammonia and bleach, it has the potential to create one of three very dangerous chemicals. One was used in WW1 (chlorine gas), and the other two are highly explosive (Nitrogen trichloride and hydrazine). However, all the victims died of exsanguination (blood loss). This isn't mentioned by Dr. Reid, who has a Ph.D in Chemistry.

Factual error: Empty Planet Episode: In the opening sequence a bomb is detonated on a bus in Seattle, in the vicinity of the Seattle Center/Space Needle. Right after the explosion, as people are moving towards the now smoking bus you can see a palm tree in the background. There are no large palm trees in metropolitan Seattle and absolutely none in this area.

Factual error: Episode Empty Planet: This episode takes place in current Seattle today (no illusions of a "Seattle in this fantasy world") including using Google earth as a means of identifying a specific area of action. But all the street signs in this episode are blue where as ALL street/interstate signs in Washington State are green with white letters.

Continuity: In Episode "Boogeyman" When the BAU is addressing the police department, Reece is standing against the wall with his arms crossed, and then immediately after his hands are in his pockets, and you see him crossing his arms.