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Understanding the causes of breath testing device inaccuracy

On Behalf of | Mar 12, 2020 | DUI

The fact that handheld breath testing devices are not always accurate has been detailed on this blog in the past. Law enforcement authorities in Camp Hill, however, continue to rely on them when enforcing the laws against drunk driving. Thus, one who is facing such a charge needs to understand exactly how the readings collected by a device could be an error. 

Many might wonder just how great of an error such a device can make. If research data is any indication, then the American Motorists Association reports that breath testing device results can have a margin of error as high as 50%. 

Assumptions made when conducting a breath test 

According to information shared by the Alcohol Pharmacology Education Partnership, breath testing devices are able to generate blood-alcohol content levels by using the concentration of ethanol on one’s breath (ethanol is the form of alcohol consumed when drinking) to make inferences about that of their blood. Specifically, it is estimated that for every measured part of alcohol in one’s breath, the corresponding concentration in their blood is exponentially greater. There has to be a baseline, however, from which to initiate that estimate. The baseline used by breath testing devices is 2100:1 (the concentration of alcohol on the blood being 2100 times greater than that of the breath). 

The trouble with assumptions 

What is troubling about this is that clinical research has showed that an average person’s blood-to-breath alcohol ratio can be between 1500:1 and 3000:1. Several unique factors can influence this, such as: 

  • Age 
  • Gender 
  • Physical characteristics  
  • Genetic makeup 

Applying a blanket assumption to blood-alcohol level testing opens up the door for incorrect readings when a person’s traits do not match those assumed by testing devices. For this reason, breath test results are often determined to be inadmissible in court. 

Pennysylvania Drunk Driving Defense: Law, Tactics, and Procedure | by Patrick F. Lauer, Jr. | Revere Legal Publishers