Understanding Blood Alcohol Concentration

Posted on: 19 November 2018


Anytime a DUI arrest issue arises, the term blood alcohol concentration (BAC) comes up. This term is often heard but seldom understood. If you or a loved one has been arrested and accused of driving under the influence (DUI), you may need to have a better idea of what this term means. Read on to learn more.

What is Meant by Blood Alcohol Concentration?

There is a bit of confusion about this term and it is frequently confused or used interchangeably with breathalyzer results. BAC is a measurement of the alcohol in your blood and a breathalyzer measures the presence of alcohol in your breath. Both of those tests have their own problems with the accuracy of the results and they can be challenged in court. Often you will hear the term BAC used to refer to either one of these methods.

How is BAC Measured?

The legal limit for intoxication is a BAC of .08%. People who get stopped on a suspicion of a DUI come in all shapes and sizes and the results of a BAC test can vary depending on body weight, sex, and how fast the suspect consumed the alcohol. That means that 3 shots of alcohol might put various drinkers either under, over or at the limit of .08%.

When a blood test for a suspected DUI charge is administered, it may take place at the police station or at a nearby medical facility. A trained phlebotomist must perform this test and that involves a blood draw from the suspect's vein. The results are not instantly available – they must be read by a lab. The results could take several weeks to become available. That means that you might be released pending the results.

BAC Level Results Can Be Inaccurate

This type of test is more than a sobriety test – it's actually a medical procedure and is subject to any number of problems. Here are but a few issues that your DUI attorney may bring to your defense:

  • The blood must be drawn by a credentialed technician who is experienced in this task.
  • The blood must be transported and stored at a certain temperature to maintain the integrity of the sample.
  • The container that holds the blood for transport and storage is known as a vacutainer, which means that it is vacuum-sealed with an expiration date. An expired canister means that the blood evidence is inadmissible.

These issues are just the beginning of things that might go wrong with a DUI stop and blood draw. Speak to a criminal defense attorney to learn more.