Breath Test

When a driver is stopped by the police and intoxication is suspected, the officer may administer ‘standardized field sobriety tests’ to determine probable cause to make an arrest. Probable cause means that the officer suspects that the driver is under the influence of either alcohol or drugs (DUI or DWI).

One likely chemical test to be administered is a breath test, commonly called a ‘Breathalyzer.’ The purpose of this test is to determine blood-alcohol content (BAC). Urine and blood tests also determine BAC. While a breath test can be administered roadside, urine and blood tests can only be performed at a law enforcement detention facility or a medical facility.

For a breath test, the officer has a small hand-held device. The driver places the mouth around a small disposable tube and blows into the device for a long breath. The officer indicates when to stop. The machine provides a result on the screen or a printout. Infrared light passing through the breathalyzer determines the blood-alcohol content (BAC) in the user’s breath. Each state has a legal maximum blood-alcohol content level.

Breath analyzer machines are fairly accurate, but they are still just estimating the BAC. If your BAC was very close to the legal limit, a slight inaccuracy could show you as illegally intoxicated when you were not. Also, some substances ingested just prior to the test can cause inaccurate readings – alcohol-based mouthwash, for instance, as well as malitol, sorbital, isomalt, and xylitol, all of which might be found in sugar-free products. Correct calibration of hand-held breath testing devices is also critical in order to produce accurate readings.

Breath-testing machines, inexpensive and convenient, are popular with law enforcement because the results are fairly accurate if administered correctly. While some states do not allow such evidence to be admitted at a trial, it is useful as a guide to officers to determine if probable cause exists for a driver to be placed under arrest.

You can politely decline to take the test, but the officer may find other ‘probable cause’ and your license will be immediately revoked for refusal. Although challenged by defense attorneys as legitimate evidence in a trial, breath testing is popular with law enforcement because it gives fairly accurate results if properly administered and it is an inexpensive form of determining blood-alcohol content (BAC).