One night, a police officer was staking out a particularly rowdy bar for possible
violations of the "driving-under-the-influence" laws. At closing time,
he saw a fellow stumble out of the bar, trip on the curb, and try his keys on five
different cars before he found his. Then, he sat in the front seat fumbling around
with his keys for several minutes. Everyone left the bar and drove off. Finally,
he started his engine and began to pull away. The police officer was waiting for
him. He stopped the driver, read him his rights and administered the Breathalyzer
test. The results showed a reading of 0.0. The puzzled officer demanded to know how
that could be. The driver replied, "Tonight, I'm the designated decoy."