by Kevin Hagen

Created on: December 11, 2008   Last Updated: December 19, 2008

An arrest and conviction for driving under the influence (DUI) is based on the evidence collected by the law enforcement office. The result of a breathalyzer test is one type of evidence, but not the only one, that can lead to a DUI conviction. You could be convicted of DUI even if the result of the breathalyzer test is below the legal limit of 0.08 percent, depending on the other types of evidence, including the officer's testimony, and possibly a video recording of your speech and actions.

If the result of the breathalyzer test indicates a blood alcohol content (BAC) of 0.08 percent or higher, you could be convicted according to a per se law, which makes it unlawful in and of itself to drive while having more than that percentage of alcohol in your blood. But the DUI law makes it an offense to drive while under the influence. Even if your BAC is less than 0.08, impairment could be proven through the arresting officer's observations of your driving pattern at the time, your slurred speech, your performance in field sobriety tests, and your appearance, independent of the results of the breathalyzer test.

The portable roadside units used to administer a breathalyzer test are generally considered to be reliable enough to be admitted as evidence in DUI cases. But the results of a breathalyzer test are based on an average person. Your sex, height, weight, metabolism, and whether you have just eaten or recently engaged in physical activity can affect the correlation between your blood alcohol content and your state of impairment. You could be considered impaired even if you pass the breathalyzer test.

If you pass the breathalyzer test, but the officer still has reason to believe you may be impaired, you could be asked to perform field sobriety tests. There are a number of possible tests, but the National Transportation Safety Administration has provided a standard model that includes three tests: the one leg stand test, the horizontal gaze Nystagmus test, and the walk and turn test. The one leg stand test requires you to raise one foot for 30 seconds, to determine your balance. In the horizontal gaze test you are asked to follow a pen or a light with your eyes. The officer is looking for involuntary jerking of the eyes, called Nystagmus. The walk and turn test involves taking 9 steps, heel to toe, in a straight line, turning, and then taking 9 steps, heel to toe, in the other direction. Any deviation from these standard tests, or the improper administration of the

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