Dirty Harry - S4-E5
Revealing mistake: After the intro at the start, it cuts to Dexter passing the fire engine, and the next long shot with a firefighter lifting the yellow tarp is a flipped shot; note the backwards licence plate, sign, etc.
Dexter (2006)
1 revealing mistake in Dirty Harry - chronological order
Starring: James Remar, Michael C. Hall, Jennifer Carpenter, David Zayas
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.
This Is the Way the World Ends - S6-E12
Dexter: I am a father, a son, a serial killer.
Trivia: Michael C. Hall and Jennifer Carpenter, who play siblings on the show, were actually married in real life, from 2008 - 2011.
More questions & answers from Dexter
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.