Dirty Harry - S4-E5
Continuity mistake: When Dexter listens to Officer Lundy's tape recording, we hear Lundy say that the Trinity killer's weight is 190 to 200 pounds. When we saw him recording that, he said 200 to 220 pounds.
Do You See What I See? - S7-E11
Continuity mistake: Deb's daily drive is an E46 '03-'06 BMW 3 series. In this episode she is in a car accident and when Dexter shows up at the salvage yard to check the vehicle he is led to an E36 '95-'99 3 series. (00:18:45 - 00:36:25)
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: Dexter goes to the morgue to see the body of his father. When he first sees the body, he bends down, and the clock behind him reads 4:11. A moment later when he stands back up the clock is at 4:17. A couple of minutes later the clock is at 4:01.
Let's Give the Boy a Hand - S1-E4
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.
Are You...? - S7-E1
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)
That Night, A Forest Grew - S2-E7
Continuity mistake: When Deb meets Lila, Lila is at the fridge and puts her arm over her breast - she isn't wearing the 'engagement' ring. However when she returns to Dexter's room it's on her finger.
Our Father - S3-E1
Continuity mistake: When Dexter gets out of the car and talks to his sister, the strap on the camera keeps flipping back and forth. (00:52:45)
Sunshine and Frosty Swirl - S7-E2
Continuity mistake: When Wayne Randall is eating ice cream, the size/amount of ice cream on the cone changes as the camera pans back and forth between characters.
Continuity mistake: The door to Dexter's apartment opens out toward the walkway. However, in all subsequent episodes the door opens into his apartment.
Shrink Wrap - S1-E8
Continuity mistake: The Ice-Truck Killer is responding to Dexter's Craigslist submission. The reply-to e-mail address is frozenbarbie@hotmail.web, but when in the new window that popped up when the ITK hit "Reply" the address is frozenbarbie@hotmail.com.
Easy as Pie - S3-E7
Continuity mistake: When Dexter and Rita are having dinner at Miguel's house, his wife drops a glass. She sets 2 other glasses on the island in the kitchen. After a cut to another shot the 2 glasses are now on the counter by the sink, before she bends down and picks up the glass she dropped. (00:39:50)
There's Something About Harry - S2-E10
Continuity mistake: When Angel is drinking with Lila after finishing her apartment, the wine glass changes position throughout the scene.
Continuity mistake: When Dexter is killing Stan Beaudry, the drop of Beaudry's blood encompasses the width of the blood slide when the two pieces of the slide are pressed together, but then goes to being roughly half the size when the shot changes.
Make Your Own Kind of Music - S8-E9
Continuity mistake: Scene with Deb and Joey having lunch. Their water glasses switch between having ice and lemon wedges, to having no ice and a lemon slice floating at the top. (00:20:15)
Shrink Wrap - S1-E8
Continuity mistake: When Doakes asks Deb "what took her so long" arriving at the first crime scene, Masuka is stood next to him. However, over the course of the conversation Masuka is seen in the background talking to another group inside the house, and in the next shot he is standing back next to Doakes. At the end of the conversation he walks over to the group inside the house. (00:05:30 - 00:06:00)
Continuity mistake: When Doakes is carrying the packs of cocaine out of the cabin, the position of his arms and the cocaine varies wildly from shot to shot. Notable examples are that the cocaine goes from being arranged in neat, accurate stacks, to being haphazardly and irregularly stacked, and back to neat again. His grip on the cocaine also varies a lot; he starts out with straight arms, then suddenly has a 90-degree bend at the elbows, and back to straight again, all depending om camera angle. All of these changes happen too fast to have been natural, and Doakes is on camera the whole time.
Continuity mistake: Dexter kills Jimenez with a chainsaw and is wearing an apron. But he gets blood all over his shirt. He leaves in a hurry after getting a call from Rita about her door being unlocked and him having the only other key. When he shows up, there is no blood on the same shirt he was wearing.
It's Alive! - S2-E1
Continuity mistake: When Batista is saying to Dexter "Did you even take my advice, Jose?" Doakes is not in the background. The next shot he is back in his spot. (00:10:00)
Continuity mistake: Near the beginning of episode 3, season 7, Dexter is attempting to take a mouth swab of a criminal in the interview room. When he first sits to request a swab from the man he is shown putting on forensic gloves. When the camera pans to him a second time to attempt taking a swab he no longer has forensic gloves on. As the man resists opening his mouth for a swab check Dexter is wearing forensics gloves again.
Answer: Two reasons. First, as a cop he knows that there are lots of murderers walking around free due to flaws in the system so he uses Dexter's "urges" to right the wrongs in the system by taking out people who have no right to walk around free. Secondly, by taking him to a psychologist he runs the risk of having him committed and he doesn't want that for obvious reasons, so he figures it is best to channel his urges to what he considers a greater good.
The_Iceman
In addition to the earlier answer, in the last season (8th) of the show, we are introduced to Dr. Vogel, whom Harry had been discussing the situation with Dexter as well, and it is shown on-camera that Harry describes what Dexter has done (killing)... So, technically he did consult a psychologist/psychiatrist, just not having Dexter and her actually meet. But Dr. Vogel was aware of whom it was and how to intercede.