A guy from Texas is having some beers in his favorite pub, later the evening he meets a nice lady together they are drinking three shots each. The lady asks him to bring her home. Sooner that night he had planed to walk home, but wanting to impress the lady he thinks about driving her home. The guy thinks about it and comes to the conclusion to drive home, because he had "only" 3 beer and 3 shots and he is used to drinking. Furthermore he believes to be under the legal BAC level.
On the way home he and the young lady are pulled over. The officers figure out very quick that our guy has been drinking and is now the driving under influence (DUI).
A test reveals his blood alcohol level (BAC) to be 0,9%, this is more then twice as high as the allowed state limit.
This would be a typical case of driving under influence of alcohol. Furthermore our guy might get problems for risking the life of the young lady sitting with him in the car.
Further problems could occur, too. For example the lady has drugs on her, he took prescription drugs early the day, maybe the lady is below the legal age to drink but looks older. These factors can easily lead to severe problems for our driver.