Preliminary Alcohol Screening (PAS) Devices

There is no question that drunk driving is one of the most aggressively prosecuted misdemeanor crimes in the State of California. In addition to the penalties associated with the criminal case, a driver in California also faces the potential suspension or revocation of their driver license from the California Department of Motor Vehicles (DMV).

Any court case or DMV Administrative Per Se Suspension will be largely based upon the “on-scene” investigation conducted by a Law Enforcement Officer. DUI arrests are most often based upon an officer making initial contact with a driver and then during the course of a DUI Investigation coming to the conclusion that the driver is impaired by alcohol. The DUI investigation most often includes a series of field sobriety tests designed to estimate a driver’s level of alcohol intoxication.

One of the most common tests administered by police officers during the course of a DUI investigation is the Preliminary Alcohol Screening test. Also known as the “PAS” test, this is a simple process of the accused driver blowing exhaled air into a small hand-held breath device.

The Preliminary Alcohol Screening (PAS) Device is classically a small “hand-held” device of plastic construction. It will have a digital LED readout and an officer will affix a small “mouthpiece” to the device before the driver blows. These devices are normally carried in a plastic case but are often thrown in the trunk of police cruisers and are frequently dropped on the ground. These devices are subject to their batteries dying or they can even be affected by Radio Frequency Interference (RFI).

The earliest versions of these devices were simple tubes or balloons that would turn a particular color to indicate the mere presence of Ethanol (ETOH) on the driver’s breath. These early versions made no attempt to estimate the actual alcohol level and therefore were used simply as a means for the officer to confirm the driver had, in fact, been drinking alcohol.

Over the past several decades, PAS devices have developed to the point that police officers now primarily rely upon the breath device in making the decision to arrest or release a driver. Police Officers will routinely arrest a driver who has blown .08% or higher on a PAS device, even though the driver may have performed all the other Field Sobriety Tests with flawless accuracy. In this instance, the officer makes an arrest based upon the presumed accuracy of a breath machine even though every “physical” evaluation of the driver indicates that he/she is not impaired.

 Are Preliminary Alcohol Screening (PAS) Devices Accurate?

California Law permits both the court and the DMV to automatically presume that the readings provided by a PAS device are accurate. Fortunately this is a rebuttable presumption which means that a driver does have the opportunity to demonstrate why the devices may not have accurately estimated a driver’s blood/alcohol concentration.

The greatest misconception of PAS devices is the belief that they accurately detect Ethanol on the human breath. They do not.   Ethanol is the active methyl-based compound in alcoholic beverages. By electrochemically oxidizing the driver’s exhaled breath, the PAS device then assumes whatever is on the person’s breath is ethanol and then conducts a mathematical extrapolation to estimate the persons’ blood/alcohol concentration. This would be fine if the only thing appearing on a human being’s breath is ethanol……….. But it is not.

This lack of “specificity” is a problem. Because the PAS devices used today in law enforcement trigger on methyl-based chemicals, a person could be stone cold sober and be arrested because the PAS device identifies another compound as alcohol. PAS devices have been known to incorrectly identify n-propanol, isopropanol, methanol and acetaldehyde as ethanol. Even a diabetic who has an elevated level of acetone on the breath could wrongly be accused of drunk driving.

In addition to the scientific problems with the PAS device, simple “mouth alcohol” can create erroneously high readings on a PAS device. If a driver has consumed alcohol, eaten food, smoked, burped, belched or vomited in a short period of time prior to PAS testing, the device can read high and the arresting officer will blindly believe the accuracy of the device.

Although police officers will tell you that PAS devices are a valuable tool in identifying innocent and sober drivers there can be no mistake that innocent people are arrested frequently because of the non-specific readings of a PAS device.

Can the Results of the Preliminary Alcohol Screening (PAS) Device be fought?

The short answer is yes. Several courts have ruled that for the numerical results of a PAS device to be introduced as evidence, there are certain “standards” that must be established. These standards are focused on such things as the officer’s training and experience as well as the maintenance and accuracy of the PAS device itself.

If you have been arrested for DUI and are facing the suspension or revocation of your driver license, call California Drivers Advocates (CDA). The DMV Defense Experts at CDA have been trained in the latest technologies of the PAS devices. Our team is comprised of former police officers who have actually worked with the PAS Devices in the field. We know where these things go wrong and we know how to keep the PAS results out of your DMV Hearing.