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Rising BAC As A DUI Defense

While everyone knows that it is against the law to drive a vehicle with a blood alcohol concentration of .08% or higher, some people may not realize that, in some situations, the greatest determining factor of a driver’s BAC is when the driver takes the chemical test. In other words, you can be driving your vehicle and be below the legal limit, but when you take a breath test at the police station an hour later, your result could be above .08%. Because it takes between 1 - 3 hours for alcohol to be absorbed into a person’s system, an individual’s BAC could continue to increase for a couple of hours after they are arrested for DUI and brought to the police station for the test.

Were you really drunk when you were driving?

Let’s look at a real life situation. Mary is at a “girl’s night out” dinner with a few friends. They eat supper and she sips her third margarita while enjoying her friends. Before she leaves, she quickly drinks the rest of her beverage which contains about .06% alcohol. Shortly after she leaves, the police pull her over and the officer smells the alcohol on her breath. Mary performs pretty well on the field sobriety tests, but the officer places her under arrest and takes her to the station to give her a breath test an hour after she was first stopped. She blows a .09% and is charged with a DUI. Mary loses her license and pays thousands of dollars in fines, fees and increased insurance costs, but she may not have been over the legal limit while she was actually driving. What was Mary’s BAC when she was driving? We will never know for sure. One thing we know…it wasn’t .09%. The body is either constantly absorbing or removing alcohol. Therefore, the BAC is either rising or diminishing. On average, it takes about an hour for the alcohol to be fully absorbed into Mary’s system and reach peak levels. This is just an average and can vary widely depending on the person. Those last several gulps probably had little effect on Mary while she was driving, but as she sits at the police station waiting to take the chemical test, her BAC has been rising. For an average-sized woman, one drink tends to raise a body’s BAC by around .03%. The conclusion is Mary’s BAC was probably closer to .06% while she was actually driving.

Police and State legislature reaction to the rising BAC defense

To combat the “rising BAC” defense, officers will begin their DUI questioning by asking the driver exactly how many drinks they had, and most importantly, when they drank them. Police also try to test a driver as soon as they can. State legislatures have helped the police by passing legislation that presumes a driver’s BAC level determined at the time of the test to be the same as when he was driving…as long as the police administer the chemical test within a specific time frame. This puts the burden of proof on the defendant. If you have been arrested for a DUI and you think that you may have a “rising BAC” defense, contact an experienced DUI attorney in your area who can look at your situation and advise you of your best course of action.