Other mistake: The marriage certificate for Rita's first marriage shows her date of birth as 04-19-1989 and Dexter states she married at 16. The marriage date is 08-16-1989, when she would have been 4 months old. She also would only be 17 at the start of the series (2006) if she was born in 1989. (00:13:45)
Factual error: When Dexter and Doakes are looking at the severed foot wearing a soccer cleat, Dexter states, "The foot was severed between the tarsus and the metatarsus." However, the foot was severed proximal to the tarsus, through the tibia and fibula. The cut was easily too high to be between the tarsus and metatarsus. (00:16:45)
Continuity mistake: In Season 3, Episode 2 during a conversation with Miguel's wife Sylvia, (Syl), and Rita in a kitchen, Syl says that they don't have any children after trying. In this episode, Syl is trying to help Dexter sell his condo and says that she downsized and focused more on "the kids."
Continuity mistake: When Doakes is about to be killed by Guerrero, the police save him by shooting Guerrero, giving him a bullet wound on his right shoulder. He is also cuffed on the ground to be arrested. However, when he is pulled up, Guerrero does not have a bullet wound anymore.
Factual error: In the police report Dexter examines, Emmett Meridian's name is followed by PhD, and yet he is referred to as a psychiatrist and prescribes medication. A psychiatrist would have an MD after his name, and a psychologist (PhD) cannot legally prescribe meds.
Factual error: When Dexter is in the hospital as a child, the doctor says that Dexter has a very rare blood type, AB negative. Although it's very rare, the people with AB- can receive donor blood with A-, B-, AB- and 0-. AB- is a very good blood-type when you need to receive blood. While it is true that hospitals normally have to use AB- because of the complexity of other proteins (and to prevent adverse reactions), in case of an emergency, like Dexter's, and a shortage, a hospital will use a blood type close enough to not likely cause a reaction. In this situation, the hospital would give Dexter O-, B-, or A- instead as blood loss would normally kill a patient long before a suitable donor could be located, called in, admitted to the hospital, and have the transfusion set up. (00:31:00 - 00:32:00)
Factual error: Dr. Meridian's victims are suicidal following withdrawal of an antidepressant, begging for more, and Dexter refers to the doctor getting his patients addicted to antidepressants. This reflects a disappointing and fundamental misunderstanding of the science of antidepressants. Even those that have "discontinuation syndromes" do not produce mood swings this wild. It is possible (though unlikely) that a random individual would have this reaction to discontinuation of an antidepressant, but Dr. Meridian would need to be in control of his victims' descent, to be sure they would become suicidal so that he could suggest the use of a gun and be sure their suicides would be successful. There are no mainstream antidepressants that would produce this effect upon withdrawal.
Audio problem: When Deb tells Angel to "look up" warning him of the security camera, Angel moves his lips as though he's talking but there is no audible dialogue. A few seconds later, his lips stop moving but then his audible lines are spoken. Then, again, there is no dialogue, but his lips move again. (00:07:15)
Factual error: When Dexter is reading the list of drugs found in the autopsy of the murder victim, one listed is "Cialopram." This is a misspelling of the antidepressant Citalopram; misspellings do not occur on drugs lists in toxicology reports, as they are computer-generated. (00:37:10)
Continuity mistake: When Dexter started removing the plastic off Travis' body, his small knife was stabbed into the chest, but during that, the sword was already stabbed into the chest, not the knife, and then again, he removed the knife from the body, and then stabbed him with the sword. (00:12:05)