Visible throughout the first season, Dexter has a large scar on his left side. Later, in season two, the scar has moved to his right side, leaving his left side unmarked.
The opening sequence in every episode shows Dexter doing his morning routines. First, he shaves and then he fixes breakfast. But at breakfast, he always has long stubble.
Dexter buys the apartment behind him to expand his space, but the exterior shots of the building show that there is no apartment behind his. It can't be next door, either, because he has a next door neighbor.
Dexter's birth year changes throughout the series: In the first few seasons, it's established Dexter was three in 1973 when his dad found him in the bloody container, meaning he was born in 1970. But in season 5 when he goes to his 20 year reunion, it says he graduated in 1991, which would mean he was born in 1973, three years after his birth year was initially stated. In season 6, Travis Marshall (played by Colin Quinn) has Dexter's license which states his birthday is 02/01/1971 now, which is the third different birth year he's had during the show.
Depending on what age Dexter is, and what actor is playing him, his eyes change color between brown, hazel, blue, and green.
In every crime scene throughout the entire series both Forensics and the detectives handle the body before the medical examiner arrives. In every state in the country, no one can touch the body until the medical examiner arrives.
Throughout the series the forensics team are seen handling crime scene evidence, walking through evidence, and/or climbing through evidence without wearing proper protective gear so they don't contaminate the crime scene.
Throughout the entire series, the forensics personnel are shown performing the duties of the medical examiner in the lab.
Throughout season 3, Jimmy Smit's character is referred to as a "District Attorney" when Florida does not use that title officially or unofficially. In Florida they are referred to as a "State Attorney" or an "Assistant State Attorney".
Throughout the series vehicles are shown with Florida license plates on the front of vehicles. Florida only issues one license plate to vehicle owners and it is always on the rear of the vehicle.
ADA Miguel Prado wears a suit jacket lapel pin of an American eagle with wings outstretching while emerging from a circular ring-frame. However, this distinctive gilt brass emblem is the 1939-1946 pattern Honorable Service Lapel Button (oddly nicknamed the "Ruptured Duck") --which was issued to World War II veterans. Miguel is shown as middle-aged and vigorous, but, had he served in WWII, he should have been at least 80 years old in the series' story year (of 2007).
All the coffee cups used through-out the series all come from the chain Smart & Final based in California. There are no Smart & Final stores in Florida.
California license plates can be seen in the backgrounds of many exterior shots.
Many characters (including killers having stuff to hide) leave their computers/notebooks without password protected logins. Only this fact allowed the story to move forward in many instances. Not only that, but all the machines are powered on with no screensavers despite more than sufficient time for them to kick in, or to go into sleep mode.
If Sgt. Doakes really thought Dexter was a psycho and up to something he wouldn't have blatantly followed him, he would have done it secretly, with a camera, and Dexter would have been caught from the start.