Understanding Blood Alcohol Content and How it is Measured

A person’s Blood Alcohol Content, or BAC, is the percentage of alcohol present in your body. The higher your BAC, the more alcohol you have in your system. The legal limit in the United States is .08% alcohol. Your BAC is dependent on a variety of factors, including your sex, your weight, the speed of your metabolism, your medications, health conditions you may have, how much food you have consumed throughout the day, and of course, how many alcoholic drinks you have had.

So how exactly is your BAC measured? Law enforcement officers use a variety of different measures and tests to determine if you are over the legal limit and thus not legally allowed to drive. If you are ever pulled over by a law enforcement officer under the suspicion that you are driving while intoxicated, the officer will probably first subject you to a series of questions about your previous activity. Where are you coming from? Have you been drinking? How many drinks have you had tonight? If after this series of questions, the officer still suspects that you may be over the legal limit, he or she will probably subject you to a combination of field sobriety tests. Examples of these tests include a walk and turn, a one legged stand, and a horizontal gaze test. If you fail one or more of these tests, the officer has cause to believe that you are too intoxicated to drive and may take you into custody and ask you to submit to other testing.

The most common test to determine your BAC is the breathanalyzer. This machine uses infrared light to determine how much alcohol is present in your body as you breathe into the machine. Since the machine cannot determine factors such as your metabolism rate and food consumption, the machine relies on a conversion factor to determine your BAC. Therefore, the number it provides is not 100% accurate, but instead a close estimate.

A much more accurate BAC test is the BAC blood test. With this test, a sample of blood is taken and the amount of alcohol present in the body is directly measured. These tests are very accurate because they need no conversion factor to estimate your BAC. However, even with their high level of accuracy, problems can occur either when the test is administered or as the sample is transported and handled.

If you are ever charged with a DUI, you should be familiar with BAC tests and how they work. For more information about BAC tests and their potential inaccuracies, visit the website of Rhode Island DUI lawyer James Powderly.