One night a police officer was staking out a particularly rowdy bar
for possible DUI violations. 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. The man sat in the front seat fumbling
around with his keys for several minutes.
Meanwhile, all the other patrons left the bar and drove off. Finally
he started his engine and began to pull away. The police officer was
waiting for him. As soon as he pulled onto the street, the officer
stopped him, read him his rights and administered the breathalyzer
test to determine his blood-alcohol content.
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."