The serial killer of serial killers... sounds kind of cheap but the series is pretty cool I think.
Any idea on the characters' type?

Some wild guesses:
Deborah: ENFj (second season spoiler)
[spoil:58aedc54ac]The instant-reaction hug she gives agent Lundy when he tells her he doesn't like Dexter more than her is something I've noticed in ENFjs[/spoil:58aedc54ac]
Lundy: IJ
LaGuerta: gamma SF
Doakes: weakest acting for Se ever
Matsuda: alpha
Rita: ISFp