This is based on the context of Series One (as I have yet to catch up. *headdesk*). Established sort-of-relationship. Dean/Carter, etc etc.
I do not own Dark Blue, or any of the characters involved. This not for profit, just for fun.
Dean knows Carter is messed up.
He knows he has issues with showing emotions other than anger and indifference, and that he seems to be allergic to thanking people for doing things for him, and that he doesn't seem to care that the intense stare he fixes on people is unsettling and has sent many of the more fragile people they've dealt with off in tears. He knows Carter interpretation of right and wrong is sometimes questionable, and that his mind doesn't quite work the way "normal" people's minds work. But then, Dean's not one to talk because he's not familiar with normality.
He knows Carter has a lot of issues with voicing his "feelings" and, other than showing people he's really pissed at them, tends to remain nonchalant about their actions and outbursts, because, hey, it's easier that way, right? Carter shies away from human contact that goes beyond work relationship and what's needed to get the work done, but Dean knows that deep down he really cares about the team – he worries about them.
He knows that Carter's a possessive son of a bitch, as shown as by his reaction to Dean's fling with Jaimie. In the office, with Ty and her hanging around behind the closed door, it was all "think of the team" and "this could cloud your judgment" and "don't let this get in the way of you doing your job, you hear me?" like any other boss scolding their employee. But as soon as they left for home, both going to their respective "normal" lives, Ty to his wife and Jaimie to her hotshot lawyer boyfriend, Carter switched pretty quickly. Heavy handed and angry, he'd shoved Dean into the wall, fucking him raw and marking his neck in a spot strategically chosen so that a shirt wouldn't hide it, so Dean wouldn't forget, so Jaimie would know, who he belonged to. If she noticed the harsh, angry mark on his neck, or the way that he couldn't walk right or sit down without wincing, or the way that Carter made a point of getting in Dean's personal space during the next case as much as possible, she didn't mention it.
If he was honest, Dean has the fling to make Carter jealous. To see how he would react if he knew Dean was with another person, a woman at that. He hadn't been disappointed.
He knows that Carter trusts him more than the other two in the team. Sure, Carter trusts Ty and Jaimie to get the job done, trusts Ty with his life and is getting there with the blonde, but Dean is different. Carter listens to Dean's advice, relies on his knowledge and intel, and trusts his judgments no matter what, like he doesn't with the others. Dean's got a theory that it's because Carter sees himself a bit in Dean – lost, alone, no strings to hold him down, nothing left to lose.
Dean knows Carter's messed up, because , truth is, Dean is too.