A man stumbles out of a bar one night obviously drunk.
He makes his way down the street knocking into everything in his path.
A police officer watches him from a cruiser across the street.
The man comes up to a parked car, fumbles around in his pockets, gets his keys, and proceeds to drive away.
The police officer, unbelieving what he saw, pulls the man over a few blocks down the road.
The man gives a breathalyzer for the officer and to the officer’s amazement the guy was stone cold sober.
“I can’t believe it! I watched you walk to this car, drive erratic all the way down the road, and my machine says you have no alcohol in your system! How can that be???”
“Oh that’s easy”, replies the man. “Tonight I’m the designated decoy.”