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Scrutinizing breath test accuracy

On Behalf of | Jun 13, 2020 | DUI

Were one in Camp Hill asked to describe the image that comes to mind when imagining a drunk driving offense, they would likely describe a scenario in which a person is standing on the side of the road undertaking a breath administered by an officer using a handheld device. Indeed, such devices are synonymous with DUI arrests. 

While most may know the near-universal impaired driving measurement (a BAC level of .08), few likely take the time to contemplate that such a measurement is of one’s blood. This prompts the question of why law enforcement officials would rely on a breath test to make a determination about a person’s blood. It also may increase the scrutiny applied to breath test results (which, according to the American Motorists Association, may have a margin of error of up to 50%). 

Measuring one’s blood through their breath 

To understand how a person’s breath offers a glimpse of their blood’s contents, one needs to know how alcohol gets on a person’s breath in the first place. Per the Alcohol Pharmacology Education Partnership, when ethanol alcohol (the type of alcohol used in most alcoholic beverages) enters the body, it is able to pass through the linings of the organs of the digestive tract via passive diffusion. It then enters the bloodstream and is eventually carried to the lungs, where it begins to vaporize into a gas when it comes in contact with gaseous oxygen. That vaporized ethanol then leaves the body as one breathes, with more than vaporizing to maintain an equilibrium with that still in the blood. 

Challenging breath test accuracy 

Knowing this may provide a basis for challenging the accuracy of a breath test result. Given that with every breath, one’s BAC lowers, using a breath measurement to determine it becomes akin to hitting a moving target. 

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