Crime and Punishment
One of the main reasons that I like series like Braquo, The Killing, The Bridge, Spiral, and Salamander is because police work is not black and white. No rules say the correct thing to do is the right decision.
Crime is a grey area, and sometimes to get the justice you need to cross that line, in the end, the question you need to answer is can I live with my choice?
Often, as in Braquo, your choice can lead to you not having the support of your superiors. But, law enforcement officers are not politicians; criminals have to be caught at any cost.