I don't think it is as simple as that.  First of all there is a time limit for taking a blood sample and where I live a warrant application would easily take that time and then some.  So what we do here is make the demand and the hospital saves a sample until a warrant is produced.  Also she didn't refuse to draw blood for him.  She was preventing him to do so.  I personally think that methodology is flawed but that is what they do there, thats what they do.  Like it or not she was obstructing him.  If he had taken the sample it is true that it would have breeched the patient's rights and the evidence would then be inadmissible and the patient would then have legal recourse.  The nurse however was interfering and while I don't condone the outcome I can see the unfair predicament the officer was put in.  The officer did confer with a superior and he acted upon that direction.  Ultimately I think that puts him in the free and clear.  His supervisor however is not.