Challenging breathalyzer accuracy

The common image associated with a charge for driving under the influence of alcohol is a person standing on the side of the road blowing into a hand-held breath measurement device. Indeed, the breathalyzer device has become so symbolic of DUI charges that many in Waco may think that a failed breath test is all that is needed to warrant a conviction. Yet in reality, breathalyzer results can often be disputed.

When a person consumes alcohol, the individual alcohol molecules permeate the lining of the organs of their gastrointestinal tract and get into the bloodstream, eventually reaching the lungs where they come in contact with oxygen and are vaporized and later expelled when the person breathes. Trace amounts of alcohol on the blood are expelled with each breath, causing more alcohol to be vaporized in order for the alcohol content in the blood to remain in equilibrium.

The blood-to-breath ratio required to maintain this equilibrium is relied upon by breathalyzer devices to estimate one’s blood-alcohol content. According to the Alcohol Pharmacology Education Partnership, breathalyzer devices use an assumed ratio of 2100:1 (one milliliter of blood has 2100 times the alcohol as one milliliter of air). Yet this assumption may not necessarily apply to everyone.

In reality, a person’s blood-to-breath ratio can vary between 1500:1 to 3000:1 depending on a variety of different factors, such as:

  • Age
  • Gender
  • Genetic makeup
  • State of intoxication

It is perhaps for this reason why breathalyzer results can be so unreliable. The National Motorists Association cites research that shows that breathalyzer devices may have a margin of error as high as 50 percent. Knowing this, one might consider challenging a case that is only bolstered by a breath measurement result.

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