If someone is pulled over on suspicion of drunk driving (DUI), the officer will conduct a series of tests to determine whether or not they have probable cause to arrest the driver. These tests are referred to collectively as “field sobriety tests,” and include:

  • Horizontal Gaze Nystagmus: the officer holds a pen or light about 12 inches from the drivers face and asks the driver to follow it with their eyes.
  • Standing on one foot:  the officer may ask the driver to count while doing this.
  • Walking an imaginary line:  the officer will ask the driver to follow an imaginary line for several steps, and may ask them to turn around and walk back, all heel-to-toe.
  • Finger-to-nose: the officer will ask the driver to close his eyes and, with both arms extended, touch a finger to their nose.
  • Reciting sections of the alphabet

Perhaps most iconic of field sobriety tests are preliminary alcohol screening (PAS) devices, commonly referred to as “breathalyzers.”

How Do Preliminary Alcohol Screening Devices Work?

Alcohol in your system is measured by what is called BAC, or “blood alcohol content.” This is the percentage of alcohol in your blood. As you drink alcohol, it is not just digested in your stomach, but rather absorbed in your mouth, throat, and lungs as well. The amount of alcohol that remains in the membrane of the lungs is relative to the amount of total alcohol in your blood.

Do I Have to Take a Preliminary Alcohol Screening Test?

Generally, these tests are voluntary, and someone pulled over on suspicion of drunk driving need not submit to them. However, it will depend on where you live and how old you are. For example, in Florida, a driver does necessarily not need to submit to a PAS test, however their license will be suspended for at least 90 days until hardship can be demonstrated. Another example comes from California, where drivers 21 and older can decline to take a PAS test without consequence, but those who are 21 and younger will be facing an automatic suspension.

Are Preliminary Alcohol Screening Results Accurate?

If used properly, and if the device is calibrated correctly, the results of the preliminary alcohol screening (PAS) test can be generally accurate, but not precise. Studies indicate that the average variance in testing results from these devices is about 15% higher than actual BACs. In fact, due to the potential for inaccuracy and the risk that jurors may believe these tests are unquestionably accurate, many states as well as courts do not permit PAS evidence to be introduced at trial.

Therefore, the results of the PAS test essential serve the sole purpose of giving the officer more concrete cause to arrest you for drunk driving and perform a more accurate sobriety test at the station.

Should I Seek Legal Help?

If you have been arrested for a DUI or similar alcohol related offense where you submitted to chemical testing, you should consider consulting a DUI/DWI lawyer immediately. An experienced criminal defense lawyer can help you secure your rights and ensure any testing was done properly and lawfully.