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How reliable are breath test results?

On Behalf of | Sep 18, 2020 | DUI Charges | 0 comments

When facing charges for allegedly driving drunk in Arizona, you may think you have few options. If authorities have a breath test indicating that your blood-alcohol content was above the legal limit of .08 at the time of your DUI arrest, challenging such a result may seem futile (regardless of how little alcohol you may have actually had in your system).

Yet that may not be the case. There is s reason why many legal professionals (both prosecutors and defense attorneys) view such the results of breath tests as unreliable. To understand why, you need to understand the mechanics of how handheld breath testing devices generate measurements.

Measuring your blood-to-breath ratio

The alcohol that you ingest eventually ends up in your bloodstream by permeating the lining of the organs of your gastrointestinal tract through a process known as passive diffusion. Eventually (after traveling throughout your body via your veins), that alcohol reaches yours lungs. Once there, a portion of it vaporizes upon coming into contact with the oxygen stored in your lungs. That vaporized alcohol then escapes your body as you breathe.

Breath testing devices measure this vaporized alcohol. When generating a measurement, the device uses a baseline assumption of your blood-To-breath ratio being 2100:1 (2100 milliliters of alcohol in your blood for every one milliliter on your breath).

Challenging breath test results

The problem with this assumption is that (according to the Alcohol Pharmacology Education Partnership), your actual blood-to-breath ratio can range between 1500:1 and 3000:1. Factors contributing to this wide range can include your gender, your age or your genetic makeup. Whatever the reason for the variation, these factors no doubt have a hand in contributing to the significant margin of error inherent with breath testing devices (which some experts estimate may be as high as 50%).