Law enforcement agencies use a preliminary alcohol screening (PAS) device to measure alcohol concentration in a person’s breath. It serves as an initial method to assess whether a driver is under the influence of alcohol.
The use of a PAS device is straightforward yet highly technical. A suspected individual blows into the device, and it calculates their breath alcohol concentration. This reading gives law enforcement a quick estimate of the individual’s blood alcohol concentration (BAC), but it is not as accurate as a blood test. The results can influence an officer’s decision to conduct further testing or make an arrest.
How it works
A PAS device uses infrared spectroscopy or fuel cell technology to analyze the alcohol content in the breath. Infrared spectroscopy measures alcohol concentration by detecting the unique infrared light absorption pattern of ethanol molecules in the breath.
When a person blows into a device that uses fuel cell technology, a chemical reaction occurs in the fuel cell sensor that generates an electrical current proportional to the alcohol level in the breath.
Legal implications
Although preliminary, these readings can justify a law enforcement officer’s decision to arrest a driver for DUI. Refusing to submit to a PAS test if there is probable cause for an arrest, can lead to penalties such as license suspension. The PAS device is often used as a precursor to testing on a stationary breath test to obtain a BAC reading that can be used in a drunk driving case.
Working with someone who can assist with creating a defense strategy is important for those who have been arrested as a result of a breath test. Under a variety of circumstances, these tests can be challenged successfully, weakening – or even destroying – a prosecutor’s case.
