Lights flash in the road up ahead. Cars slow to a crawl and for a moment you wonder what's happening. Then you notice how many of the flashing lights are red and equal distance on both sides of the road.
This is a DUI checkpoint. You flashback to the restaurant, the amount of wine you had, and how long you were there. You feel fine, but that isn't an indicator. You roll down the window and answer a few questions. The officer indicates they want to check your BAC. But what does BAC mean?
Let's look at BAC and the tests police use to determine a driver's alcohol level at sobriety checkpoints.
What Does BAC Mean?
BAC stands for Blood Alcohol Concentration and represents the amount of alcohol in your system. BAC tests reflect the grams of alcohol per 100 mL of blood.
State laws differ in exactly what counts legally drunk or impaired for the purposes of driving. The general legal BAC comes down to .08% for driving a typical vehicle. Those driving commercial vehicles, on or off duty, are capped at .04%.
How is BAC Measured?
BAC can be tested for in a couple of ways. Remember also that alcohol can be detected in different materials for various lengths of time.
The most common test given at a checkpoint is the breathalyzer. This test doesn't actually directly measure BAC, alcohol concentration in breath isn't the same as blood. The test looks for lightwave refraction and absorption with an infrared spectroscopic analysis.
The computer inside the machine equates this to a BAC. This is why it is important to confirm these results, after an arrest, with a blood test.
Blood tests rarely get performed at checkpoints as they are difficult to do outside of controlled circumstances. Many people do not like facing a needle or the possible issues associated with fear or contamination. Police employ certified blood specialists, called phlebotomists, to do blood draws.
Blood tests take time to be analyzed, normally about three to four weeks. Other tests employed can include urine (viable for upwards of three to five days using an ethyl gluconoride index) or hair.
Hair tests don't come into play unless a person is looking at a repeat DUI offense and were court ordered not to drink. Often these types of restrictions also get a person sent to a treatment program or they're required to take online alcohol classes as part of a conviction.
What Is a Rising BAC Defense?
In cases where BAC was over the limit at the time of driving, defense attorneys frequently use a "rising BAC defense" at trial, meaning you were under the legal limit when you drove, but your BAC levels escalated since the alcohol was being absorbed in your system at the time of testing.
Metabolism rates vary for men and women based on many factors, such as ethnicity, body fat, age, medications, and how much you have eaten. Regardless of how quickly you absorb alcohol, it will take 0.0156 BAC per hour to burn off.
Now that you have a better understanding of what BAC means, you'll know what to expect if you run across a DUI checkpoint and are asked to submit to a breathalyzer test.
Have you been assigned by the court to take an alcohol class as a result of a DUI conviction? If so, we're here to help. Check out our website for information on our online alcohol classes for each state and contact us for more details.
NM Online Educationis a premier defensive driving, DUI school, and alcohol and drug evaluation counseling center. We provide a wide variety of online classes to satisfy your court or DMV requirements. Offering classes in ALL 50 states, we're a leader in U.S. distance learning programs.