When Richard is talking to the stewardess in the bar, he asks the bartender for a cigarette and breaks off the filter leaving tobacco hanging out. When he turns to the stewardess and asks for a light, the cigarette is whole again.
When Richard is arguing with his wife while eating spaghetti, his plate is full when he slaps her. After she gets up and walks away arguing, they cut back to Richard and his plate is nearly empty.
In the film Richard is depicted as shooting some of his victims, when in fact Speck either strangled or stabbed all of his victims.
Richard is shooting pool with a guy wearing glasses, the guy is aiming his stick to the orange 5-ball instead of the cue ball next to it.
When Speck is riding the train, we hear sounds as if the train is passing railroad crossings. However, by looking at the windows we can tell that the train is not moving.
When Sondra hides under the bed her restraints are so loose they almost fall off.
When Richard is strapped to the gurney and is yelling "Fight me fair" during his tantrum, he could easily get out the wrist restraints because they are loose.
In the building where the murders take place, we see fire alarm and smoke detection devices that would not have been present in 1966.
A number of items in the hotel would not have been present in 1966. These include electronic card locks on the room doors, as well as a fax machine, a computer screen, and a laser-printed sign behind the front desk.
The newspaper clippings Richard Speck has taped up in his prison cell appear to be contemporaneous with the time the scene was actually filmed. One visible headline, "Suspects jailed in filmlike bank job," coincides with a Los Angeles Daily News story of September 16, 2006. Another headline, "Congress asks 4 to testify in HP probe," fits with a spying scandal during the same month that involved executives at Hewlett-Packard and information leaked from its boardroom.