Most people have a casual familiarity with the experience of being pulled over by police and being arrested on suspicion of driving while intoxicated. If the experience isn't first hand, chances are they have seen representations of it on television. The accused may be asked to participate in a field sobriety test, which often involves some sort of balancing act. They might be asked to take a breathalyzer test that involves blowing into a contraption meant to measure blood alcohol content. They might also be asked to submit to a blood test.
It is becoming increasingly common that people charged with DUI were not drinking at all. In this day and age, more and more people are prescribed with prescription medications, particularly pain medications. They are taking this medication legally and as prescribed by their doctor and do not realized that if pulled over by a police officer, a DUI arrest could be the result.