Minor spoilers below, though I’ve tried to be as vague as I can while making my points):
It occurred to me on the bus today that while on the surface the Shield and Dexter are very different shows, there are some striking similarities (likely coincidental for the most part, but fun to think about).
For the uninitiated, The Shield focussed on a dirty cop (Vic Mackey) and the world around him; it was gritty real and full of action, very past paced. Dexter is about a forensic cop (Dexter Morgan) and the world around him. Dexter is also a serial killer and his adventures tend to be a lot slower paced, with the occasional flight of fancy; Dexter is also meticulous than Vic, less prone to snap decisions. The Shield also lets action and dialogue determine people’s thoughts, whereas you frequently hear Dexter’s thoughts. So they are quite different shows in many ways.
But here are some similarities:
1. Both shows focus on a corrupt cop, with sub-plots involving a strong supporting cast whose adventures may or may not involve the lead at any given time.
2. Both show’s leads frequently have to cover their crimes from other cops.
3. Both show’s leads often act heroically and selfishly in the same episode.
4. Both show’s leads have a code that they live by, which is not to the letter of the law.
5. Both show’s leads break their code at least once during the series, but try not to.
6. Both show’s leads have certain compulsions and would not be content sitting at a desk all day.
7. Both show’s leads at some point have at least one other cop suspicious of them.
8. Both shows have a somewhat comedic co-worker who is easily underestimated by others.
9. Both shows have at least at least one other cop in the police force who has broken the law.
10. Both shows have had a single season where a previous Oscar winner was a cast member.
11. Both shows have a bit of a tendency to show male backsides, though not the leads’ (neither sex gets off scott free here but it seems to happen to men more).
12. Both shows have in some seasons a tough as nails black woman as a boss figure (lieutenant or captain)
13. Both shows’ captains (the ones above) have a cop as a confidant who is not the lead.
14. Both shows challenge the viewer to decide how moral or immoral the main character is (to a degree this is also true of supporting characters, but the latter's more pronounced on The Shield than Dexter).
15. Both leads have at some point in their lives been married.