As it is for most people in Georgia, your association with a criminal charge for drunk driving is a person standing on the side of a road blowing into a hand-held breath testing device. If and when you happen to find yourself being the one taking such a test, one particular question may dominate your thoughts: why would law enforcement choose to measure your breath to determine your blood-alcohol content?
It is a fair question, yet one that likely has an answer given the reliance on breath-testing devices to support DUI charges. Once you understand how alcohol gets on your breath, however, you may be in a better position to challenge the results of the breath test in your case.
The pathway of alcohol from a drink to your lungs
The exact form of alcohol used in beverages is ethanol, which is a water-soluble compound. This fact is important because it means that after ingestion, ethanol molecules can permeate the lining of the organs of your gastrointestinal tract through a process known as “passive diffusion.” This allows them to enter into your veins, which transport them throughout your body in the bloodstream. Per the Alcohol Pharmacology Education Partnership, the ethanol-saturated venous blood eventually reaches your heart, where the right ventricle then pumps it into your lungs. Upon coming into contact with the oxygen in your lungs, some of the ethanol vaporizes into a gas, which then leaves the body when you exhale.
Hitting a moving target
This process continues gradually, with the content of alcohol on your breath maintaining equilibrium with that in your blood. Yet since this changes with each breath, breath testing devices have to assume a static blood-to-breath ratio when generating measurements. Comparing the discrepancies possible when using a fixed value to try and estimate a dynamic process may lend weight to your argument against the reliability of your breath test.