The mind boggles?

The police car was sat in a lane near a public house just waiting for a likely candidate to come along to make their long vigil worth while. As the Pub started to empty their wishes were granted? One of the car drivers was having difficulty getting into his car. Eventually the car door opened and the driver slid into the seat. The two policemen couldnt believe their luck. The car driver firstly tried the lights and then the 'flashers' and soon the car was started. It moved forward and stalled. The driver then got out and wiped the window and then got back into the staionary car? The lights were on and the flashers were 'flashing' 'left and then right'. The car stated to move towards the exit from the car park. The Policemen were intoxicated by the excitement the driver had generated. As the car reached the road the police car followed it for some little distance before using the 'two's and blue's. The car stopped imiediatly and the Policeman ran toward the car to stop the driver getting back into the traffic from the public house and causing an accident. As the car park emptied the policeman asked the driver to get out of the car? "I am of the opinion that you are unfit to drive Sir" and I would like you to take a 'breath test' now. The driver didn't object and as he 'blew' into the litle white tube the polceman watched, quite sure that he had a 'catch'. Upon the driver completing the test the Policeman looked at the little marker that would tell him if the driver was drunk or sober? The sightglass said 'negative' and the policeman said to the driver that he would have to take him to the 'Station' for a proper test as the 'bag' was defective. The policemans face was a picture as the driver pointed out the fact that the 'bag' was not wrong as he was the 'nominated decoy' for the night?