How Reliable Are Breath Tests?

In California, one way you can be charged with (and possibly convicted of) a DUI is when you drive a vehicle with a blood alcohol concentration (BAC) of 0.08% or more. Law enforcement officials can use three different tests to measure your BAC: breath, blood, or urine tests. And while a blood test is often considered the most accurate of the three and directly measures BAC, most often breath tests are administered. The reason for this is that breath tests are more economic.

With a blood test, you must have your blood drawn, and it must be done by a trained professional. Additionally, because this method is invasive, law enforcement officials need a warrant before administering it.

With a breath test, there is no warrant requirement, and all you have to do to provide a sample is blow into a machine.

But are the results of a breath test 100% accurate all of the time? Not necessarily. The New York Times reported that many breath analyzers throughout the U.S. produced skewed results. The fact that breath tests can be inaccurate, and the results of the Times's investigation, is concerning because many DUI cases hinge on these results. Thus, an innocent person could be convicted of a crime, even though they had committed no offense.

How Do Breath Tests Work?

When you drink an alcoholic beverage, the alcohol gets processed through your system and absorbed into your bloodstream. As it travels your body, it passes through your lungs. When you breathe out, you also expel some of the alcohol in your system.

A breath test measures the amount of alcohol in your lungs. The results are only an estimate of your blood alcohol concentration.

What Factors Can Influence Breath Test Results?

As mentioned earlier, breath tests aren't always accurate. In a way, these are sensitive machines needing delicate care and handling. Any number of things can produce skewed results.

Some of the factors that can produce a falsely high blood alcohol concentration include, but are not limited to:

  • Substances present in the mouth: Breath testers are designed to estimate BAC by analyzing the molecular structure of alcohol. But several other substances can have a similar makeup as alcohol.
  • Poor machine calibration: For a breath analyzer to work correctly, it must be calibrated frequently. According to the New York Times report, poor calibration led to results that were elevated by 40%.
  • Software glitches: A problem with the breath machine's operating system can cause skewed results.
  • Improper procedures followed: If the breath test operator does not follow proper procedures or does not know how to use the machine, the results may show that a person had a BAC over the legal limit when in reality they didn't.
  • Physiological variables: Certain health conditions, such as diabetes, and diets can produce results that don't accurately reflect a person's BAC.

Some safeguards are in place to prevent errors that can lead to inaccurate results. For instance, Title 17 of the California Code of Regulations requires any agency that administers chemical tests to determine BAC levels to follow specific protocols.

A few of the rules that must be followed include:

  • Calibrating the machine after a certain number of days or uses
  • Allowing only trained individuals to administer the test
  • Observing the driver for 15 minutes before taking a sample
  • Taking at least 2 breath samples
  • Keeping accurate records of calibration times and results

Although Title 17 procedures are in place, violations can and do occur, leading to inaccuracies.

Were you subject to a breath test after a DUI arrest? Our attorney will review all records and reports associated with your case to identify any issues that might have affected your results.

To schedule a free consultation, call Koenig Law Office at (661) 338-5353 or contact us online. We serve residents of Bakersfield and the surrounding areas.

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