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Just how accurate are breath tests?

Over the past few decades, the fight to make driving safer for both vehicle operators and passengers has focused on reducing the number of people driving under the influence. The strategies used by law enforcement and the legislature have been broad, including public education, increased penalties for driving under the influence, and increased enforcement and detection. One of the keys to that success has been the rise of breath tests for drunk driving. As more and more data is gathered on those devices, though, it is becoming increasingly obvious that there are serious questions about their reliability and their results.

Major issues with handheld breath test machines

All breath test machines have the same fundamental issues, but the larger the device is and the more detailed its analysis, the more accurate it is. However, the following issues can make handheld test results less accurate:

  • Failure to recalibrate the machine for the current temperature
  • Hemocrit variations-that is to say, the volume of red blood cells in a person's blood is assumed to be at one level with most breath tests, and it is actually a range, the far sides of which might cause a sober driver to read as intoxicated or vice versa
  • Acetone and other methyl subgroup compounds that are detected as ethanol by the machine due to chemical similarity

For these reasons, it is always recommended by both the manufacturers of the handheld devices and the law enforcement community that the handheld results be confirmed with a larger machine at the precinct.

Sober drivers are penalized

When these inaccuracies affect breath testing, sober drivers wind up paying the price-especially those with health conditions that affect their hemocrit levels or that cause their bodies to produce more methyl subgroup compounds. These compounds are natural in the human body-saliva regularly contains more than 70 of these compounds. Properly calibrated machines assume certain quantities of these compounds, but people with rare health conditions may find themselves in a position where their body naturally produces the compounds that mark them as intoxicated when they are, in fact, sober.

When a test shows a driver is over the limit

The best thing to do is to request a lawyer right away if one is facing a breath test result that leads to an arrest. Then, it is advisable for a person to wait for the attorney before saying anything. Experienced attorneys understand the issues with breath testing and the options available to drivers who are accused of operating a motor vehicle while under the influence.

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