What aspect of breath specimens is crucial for legal determination of intoxication?

The legal determination of intoxication primarily relies on the alcohol concentration present in a breath specimen. This measurement is crucial because it quantitatively indicates the level of alcohol in the individual’s system at the time of testing. Laws regarding driving under the influence (DUI) often specify legal limits for blood alcohol concentration (BAC), and breath testing devices, such as the Intoxilyzer 9000, are designed to estimate BAC based on breath alcohol concentration.

While the volume of breath and the time of expulsion can play roles in the testing process, they do not directly define intoxication. The "quality of air" could relate to how clean or uncontaminated the breath sample is, but it is not a key metric used for legal standards like alcohol concentration is. Thus, the emphasis on alcohol concentration reflects its direct relevance to legal thresholds that are used to assess whether a person is operating a vehicle in a manner that is unsafe due to alcohol influence.