There are two breath tests that law enforcement will ask you to take to determine your blood alcohol content. The first test is known as a preliminary alcohol screening (PAS) test and this occurs before you have been arrested. The second is a breath test that occurs following an arrest. The difference between these two tests is that, unless you are under the age of 21 or have a prior DUI, you do not have to take a PAS test.
PAS Tests Can Cause More Harm Than Good
PAS tests are generally given on a handheld, roadside breathalyzer device. This device works by testing the small amount of alcohol that is excreted into the lungs after drinking. This is not a direct indication of how much alcohol is in the blood, but uses a mathematical formula to convert the amount of alcohol in the breath to an equivalent BAC. Because it is not an exact measurement, breath tests are considered to be less reliable than blood tests.
In order to maintain accuracy, breath tests must be constantly regulated and calibrated, with strict rules regarding who is able to operate the machinery and the types of maintenance that can be performed on the device. PAS tests are not subjected to the same restrictions as post-arrest DUI tests, making them even less accurate.
The purpose of the PAS is to help an officer decide whether or not to make a DUI arrest. Like field sobriety tests, you are able to refuse this test without any legal consequences. Law enforcement generally will not lead you to believe that this is an optional test and present it as mandatory. However, if you submit to this test, you can have the results used against you in a criminal case. Unless you are restricted from refusing, passing up a PAS test may be in your best interests.