Visible crew/equipment: You can see the cabin door open on Dexter's boat, and a crew member getting out while he is driving the boat, supposedly alone. (00:45:45)
Continuity mistake: Deb moves in with Dexter to his apartment in a 2nd bedroom during season 2 following the ice killer's kidnapping and attempt on her life. But in Season 5 when they try to share this apartment again, it's only 1 bedroom now?
Continuity mistake: When Lumen stabs Dexter with his knife in the swamp, she hits right above his elbow which he grabs promptly. When the camera angle changes, he's now grabbing his upper arm that's bleeding from a different spot than where he was stabbed.
Everything Is Illuminated - S5-E6
Continuity mistake: Lumen has a dark "H" shaped scratch on her right shoulder. A few minutes later, its turned 90°, like a sideways "H," and it is very faint. (00:22:05 - 00:32:35)
Character mistake: Searching for clues to identify a suspect, Masuka takes fingerprints from the interior of a truck. Back at the lab, he says he had two dozen prints and they all belong to the same person. Unless the prints are all of the same FINGER, there is no way he could know the prints were all from the same person without a suspect to compare them to. Masuka is a forensic expert and should know better. (00:15:40)
Other mistake: Lumen agrees to meet her former fiancé Owen at noon. When they meet up, the sun setting in the background indicates that it's evening. (00:16:12 - 00:23:39)
Factual error: When Dexter is punching Olivia's father in his left side, he says "That's your liver." Only the liver is on the right side. For a serial killer who routinely dismembers bodies, Dexter should know which side the liver is on. (00:42:50)
Revealing mistake: When Dexter stomps on Barry's kidney, you can see his foot doesn't even make contact with Barry's body.
Revealing mistake: When Dexter is fighting Liddy, in the van after kidnapping Dexter, the knife is a rubber fake knife. (00:38:15)
The Big One - S5-E12
Continuity mistake: When Dex gets the phone-call from the city archives he steals a red Pontiac Grand Am GT. When he crashes it at the camp it's a badly-painted orange Chevrolet. (00:21:00 - 00:28:00)
Suggested correction: The car is a red Pontiac but it is a Grand Prix, not a Grand Am.