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What you need to understand about breath test accuracy

If you have been suspected of driving under the influence of alcohol, you have almost certainly faced a breath testing device at some point or another. Over the past half century, they have become almost ubiquitous symbols of law enforcement, and with the invention of the ignition interlock exchange, they are even being used to enforce drunk driving penalties in some areas. You would think that such an important law enforcement tool would be rigorously researched and designed to be as accurate as a blood test, or more so, based on the way they are relied upon, but that is not actually the case.

In fact, more and more courts are finding that there is evidence the breath test results are prone to wild inaccuracy, especially when it comes to cases that are borderline. One court in California went so far as to rule that defendants in that state have a right to challenge breath test results. Here is what you need to know.

Why alcohol breath tests are sometimes inaccurate

The first thing to understand about breath tests is that they are not actually inaccurate-they measure what they are designed to measure. It i s just that what they are designed to measure is not as simple as "whether your blood alcohol content is too high." What they actually measure is the content of certain methyl subgroup compounds in your breath. Based on that information, the average blood volume of a human being, and the air temperature, it is able to make an estimate of your intoxication level.

The problem is that those factors that its reading depends on are not constant. Devices can produce inaccurate results due to any of the following reasons:

  • Blood volume, or hemocrit levels, that differ substantially from the average
  • The presence of acetone or other non-ethanol methyl subgroup compounds in your breath
  • Failure to recalibrate the machine for the proper temperature

If any of these situations happen, you could wind up under arrest for a DUI without being intoxicated.

If you are arrested

Remember to ask for an attorney right away if you face arrest on charges of drunk driving. Experienced DUI attorneys will be familiar with the issues surrounding breath tests, and they can help you understand how to best defend yourself. Without the right legal help you are left to navigate the criminal justice system alone, and that means you may not know all the options available to you to help your defense.

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