Drunk driving

The policeman had the bar under surveillance a few minutes before closing time, so he could see who comes out drunk.

The first one out the door at 2:00 o'clock weaved down the sidewalk, then fell on the curb. Sluggishly got up, then tried his keys in five cars before finding his own car.Once inside his car, he fumbled with his keys for 2 or 3 minutes.

Meanwhile, all the club patrons had gotten into their cars and driven away, leaving this one fellow quite alone in the parking lot.

Finally, he got his car started and began to very slowly drive away.
Immediately, the police car was behind him with lights flashing.
The policeman asked the man to take a breathalyser test, to which he readily agreed.
When the reading was 0.0%, the policeman said, "How can this be?"

To which the man replied, "Because tonight, I'm the designated decoy."