This is how it was back when I wore the blue uniform. We had the hand held breathalyzer and would use it on suspected drunk drivers. If they tested positive on it they would be arrested and taken either back to the police department for a certified breathalyzer test or to the hospital for blood work. Their choice. Some would choose the blood work hoping the hospital was busy and it would take a while before their blood was drawn so their numbers were decrease. It didn't work out for them since we went to the front of the line for blood work, we just didn't advertise that to the public. LOL
Not sure if many departments still do it that way or not, my days were back in the 80's and 90's.
TM