Criminal Law Basics: An Introduction To Drug Charge Defense

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What Blood Alcohol Concentration Means for Your DUI

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The term blood alcohol concentration (BAC) comes up often when discussing driving under the influence (DUI) issues. You should know that this term can apply to two very different measurement methods and that the results are far from reliable. Read on to learn more.

Breathalyzer Results and BAC

Many people, law enforcement and judicial personnel included, use the results of the breathalyzer interchangeably with an actual blood test. The breathalyzer is a portable device used to measure the presence of alcohol in the air you breathe out. The results are often misinterpreted, and if there is any chance that you have been arrested because of an inaccurate result from a breathalyzer, you must speak to a criminal defense attorney right away. If you "blow" anything at or above .08%, you can be arrested for DUI. These results are highly arbitrary and don't take into account the sex, weight, metabolism, or anything but the metabolized alcohol exhaled in the breath at the moment of the test.

Blood Tests and BAC

If the results of the breathalyzer and/or the field sobriety tests are inconclusive, you might undergo a blood alcohol test that requires blood to be drawn. The potential for mistakes is high, and the results can be particularly inaccurate when the test is not performed at a medical facility and by a trained phlebotomist. This form of testing is not usually performed by law enforcement and a warrant may be needed in some locations. You might remember the case of the emergency room nurse in Utah who refused to allow a blood test for the presence of alcohol (or other illegal substances) on an unconscious suspect because the detective had no warrant. When this type of test is performed, the results are not immediately available. There are several prerequisites for a blood test, including:

  • the technician must be trained, credentialed, and experienced
  • there must be a legal reason to do the draw (warrant, probable cause, consent, etc)
  • the evidence trail must not have gaps (how the sample travels from the test site to lab)
  • the container used to transport the blood to the lab must be vacuum-sealed (they all have expiration dates)
  • the integrity of the sample must not be affected by temperature fluctuations or extremes

As you can see, there are too many issues with blood draws and breathalyzer results to just trust the evidence in your case. Speak to a DUI lawyer who understands what is at stake with your DUI case.