If you haven't seen it. Wow!
So now for my take on this.
Why did the police want the patient's blood so bad in the first place? Because a neighboring police department wanted it. Why did they want it?
Because he was badly injured in a head on collision by a suspect in a high speed pursuit. The police were actively chasing the guy that injured this poor fellow.
The only way this makes sense is that the police were trying to find any evidence possible to cover their ass.
So in an effort to cover their own ass, they arrest this poor nurse. Shameful. It's so ugly.