PAS Testing in DUI Cases: What you need to know.
PAS testing, or “Preliminary Alcohol Screening” testing, is an investigatory tool used by police in DUI cases. Of dubious scientific validity, PAS tests can be used to either test for the “yes/no” presence of alcohol, or, if certain scientific safegaurds are followed, can be used to determin
e the blood alcohol concentration of a person by measuring their breath alcohol.
PAS Tests: The right not to submit a PAS test.
PAS testing is not mandatory… meaning you can refuse to submit a breath PAS test. This is different from an “evidentiary” test (sometimes known as “evidential” test) that is mandatory if you are arrested for DUI. Law enforcement is required to admonish you and let you know that you have the right to refuse the PAS test. (People on probation for DUI’s are required to submit a PAS sample if asked by law enforcement.)
How a PAS testing device works: The dubious science of measuring a person’s blood alcohol level.
The PAS device works by measuring a person’s breath for the presence of alcohol. In theory, laser light shined through alcohol will reflect in a certain way, allowing a machine to measure alcohol by shining laser light into it. The numeber that is measured is alcholo particle in the person’s breath. As you probably already figured out, this is not a direct measurement of the person’s blood for the level of blood alcohol. The person’s blood alcohol content is then “dervied” or calculated using the breath measurement. The process of determinining a person’s blood alcohol content from breath done using a “partition ratio” that the breath measurement is multiplied with. The “partition ratio” is very problematic because it assumes all people are the same. They are not. The proper partition ratio varies between the sexes, between races, between invididuals and even varies in the same individual depending on their current metabolism.