Given the extent of police misbehavior common in the US, if I were a juror, I would never trust a blood sample 'drawn by police' any more than a picture of a gun lying by a dead person as evidence that he was aiming it at the officer.  We all know a percentage of cops carry a throw down gun to justify police malfeasance.
As a strong believer in law and order, I am disgusted at the numbers of police that violate citizens and destroy respect for police and our justice system.
There are bad people and too many of them are in the police forces due to poor screening and hiring by chief who are themselves power mad and looking for an excuse to use violence.