On our DUI forum we recently had a question from a driver who was arrested at 4:00 A.M. but did not submit to a blood alcohol concentration (BAC) test until 5:00 A.M. then again at 5:30 A.M. The driver wondered whether their blood alcohol concentration would have been higher at the time of the chemical test than it would have been at the time they were driving.
What is your blood alcohol concentration?
Before we answer this driver’s question it is important to understand what we mean by BAC or blood alcohol concentration. A driver’s BAC is the amount or weight of alcohol in a driver’s blood, expressed as a percentage. It is illegal to operate a motorized vehicle with a BAC of 0.08% or higher in all states.
BAC is measured through a urine, breath or blood sample. Blood is generally assumed to be the most accurate test. Because so many factors affect a person’s intoxication level (i.e. their weight, metabolism, and amount of food eaten) many drivers may consume only a few drinks and become illegally intoxicated.
Other factors affecting intoxication
As mentioned above, the main factors affecting a person’s intoxication levels includes their sex, their weight, and the amount of food they have consumed. Other factors which are also crucial to determining whether a driver is intoxicated are the amount of time it takes for the alcohol to leave the body and how fast the alcohol can be metabolized by the liver.
For instance, experts estimate that 10 percent of ethanol leaves the body through sweat, breath and urine. The remaining alcohol must be metabolized by the liver. Generally, it takes a driver approximately an hour to break down a one half ounce of ethanol. For example, a blood alcohol content of 0.05% would take approximately three hours and twenty minutes to metabolize out of the body.
Was I intoxicated at the time of my DUI arrest?
With the information above it is easy to see that since it could take up to 3 hours for alcohol to be absorbed and metabolized from your body, it may be possible that your BAC would continue to rise after you are stopped and arrested for DUI, with the absorption rate highest at the time of a delayed chemical test.
For example, if your chemical test was not given until an hour after your DUI arrest and it registered a result of 0.12%, it may be possible that your BAC was only about 0.07% at the time you were operating your motorized vehicle. DUI lawyers may review your testing information and use what they call the “rising BAC defense” to counter claims that you were intoxicated at the time you were driving.
What states have begun to do, however, is to develop laws that create a presumption that the defendant’s BAC level at the time of testing was the same as when they were driving, as long as the officer performs the test within a specified time period. So, if the officers followed the laws of your state and performed the tests within the predefined time limits, it may be up to you and your DUI lawyer to prove that your BAC could not have been as high when you were driving as it was during your BAC test.
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