The following scenario is becoming more and more prevalent in Arizona. A person is pulled over for some very minor driving offense (like having a license plate light out or turning into the middle lane and not the curb lane), and a police officer approaches and asks if they've had anything to drink. The person then honestly answers that they've had one beer with dinner. That person trusts police officers, so, even though they do not believe they were driving while impaired, they comply with every request, hoping to be let go, only to be told that they've failed all of the balancing tests and are being arrested for suspicion of driving under the influence. The person's car is then towed, and he or she is taken to a police station and held until a phlebotomist arrives and draws his or her blood. The person's blood alcohol level is accurately tested, and it comes in as expected: way below the legal limit, perhaps a 0.00 BAC.
As a DUI defense attorney, I have been in many crime labs, and I've yet to see one that looks anything like those portrayed on TV. Unlike 'CSI', the local crime lab is not 40,000 square feet separated by glass walls. Frankly, it would be bad science to build labs that way.