During the pilot episode Dexter enters his apartment via an outwardly opening front door, then for the rest of the seasons it's an inwardly opening door.
In the first episode when Dexter is giving a doughnut to Angel, Angel is seen wearing a gold badge on his hip which was later said to be given upon his promotion to sergeant.
The actor who plays the young Dexter has two prominent moles on the right side of his face, near his lips. Adult Dexter does not have moles in that area of his face. Also, young Dexter has blue eyes whereas adult Dexter's eyes are green.
The air conditioner changes brand names. The Pilot shows it as an LG, but the next episode it is changed and then back to LG later in the season.
In the pilot, Dexter's car is a silver Dodge Neon. However, in later episodes it is replaced by a silver Ford Taurus with no explanation or indication that he had purchased a new car.
The dissected bodies of the victims show just one bone in lower part of the legs, while in reality they are two, the tibia and the fibula.
Police cars in the series are green and white. In Florida only Sheriff deputy's cars are green by law.
Firefighters shown throughout the series are Los Angeles City or county firefighters. Only western US firefighters wear the style helmet shown.
When Angel is showing Dexter the second "bloodless" crime scene, the bone sticking out of the leg has visible seams along it from where it was cast, indicating a plastic prop rather than an actual bone.
At the crime scene Lt. Maria Laguerta is standing in front of two reporters holding two microphones with station logos on them, but there are no TV-cameras.
When Dexter goes to the www.screambitchscream.com website, the cover page has a warning which says "You must be 21 to enter", and a warning at the bottom of the same page stating "This site contains extreme material. By entering, you acknowledge that you are at least 18 years of age.". This is inconsistent.
The boys choir in the opening scene consists mostly of adolescents, some even showing facial hair. Their voices cannot be as high as the soundtrack suggests.
Characters frequently walk to their cars and their windows are down. No one in Florida leaves their windows or their top down as rain is frequent and hard to predict.