PAS Test – Preliminary Alcohol Screening Device

A PAS test (preliminary alcohol screening) is a roadside breathalyzer test police give you if they suspect you of driving under the influence. A handheld device measures your blood alcohol content (“BAC”), and officers use the results to determine whether to arrest you for DUI.

The biggest difference between a pre-arrest PAS test and a post-arrest chemical test is that the PAS test is entirely optional unless:

• you are under 21 years old and suspected of violating California’s “zero tolerance” law for underage drivers, or
• you are on DUI probation (for a prior DUI).

If you do not fall into either of these categories, you may refuse a PAS test without consequence (which we advise you to do). This test is simply an optional tool – like a field sobriety test – that can help a police officer decide whether to arrest you for DUI. Plus, the results can be used against you in court.

However, if you have been placed under arrest, refusal to take a DUI chemical test could result in:

• the loss of your license, and
• enhanced DUI penalties.

For more information on this subject, please see our article, the consequences of refusing a DUI blood or breath test.

We are a firm whose lawyers include former prosecutors and cops. We now use our law enforcement experience to defend people accused of DUI throughout Southern California.

To help you better understand PAS breath testing, our California DUI attorneys discuss the following, below:

• 1. What are the PAS testing procedures?
• 2. What equipment is used?
• 3. Special Rules for Under-21 Drivers
• 4. Special Rules for DUI Probationers
• 5. How do PAS tests measure BAC?
• Additional Resources

1. What are the PAS testing procedures?

When an officer suspects you of driving while intoxicated, they will begin a California DUI investigation.

As part of this investigation, you may be asked to take a preliminary alcohol screening (“PAS) breath test. This test is optional unless:

• You are under 21 years of age (Section 3, below), or
• You are on probation for a prior DUI offense (Section 4, below).
  

If you are actually arrested for DUI, however, refusal to take a post-arrest DUI chemical test can result in:

• a minimum one year driver’s license suspension, and
• enhanced penalties if you end up being convicted of DUI.¹

By law, the police are required to tell you that a PAS breath test is optional.² Often, though, they will present it as if it is not a choice.

The results of a PAS test can be used in trial to help secure a DUI conviction. Accordingly, we advise that you politely refuse to take it if you are at least 21 and not on DUI probation.

Mouth Swabs Instead of PAS Tests

Some counties — including Los Angeles — have begun conducting limited tests of saliva swabs for preliminary DUI testing for drugs and alcohol.³ These tests are equivalent to the PAS breath test, except that the results are not – at present – admissible in court.

Unless you are under 21, or on DUI probation, you may legally refuse a mouth swab without consequence.⁴

When an officer suspects you of driving while intoxicated, they will begin a California DUI investigation.

2. What equipment is used?

A PAS is given on a handheld, roadside Breathalyzer or similar device.

A post-arrest DUI breath test, on the other hand, is usually given on a desktop device at the police station. Or, if you are arrested at a DUI checkpoint, it may be given at a mobile police unit.

In some counties like Orange and Ventura, post-arrest breath tests are given on the Evidential Portable Alcohol System (“EPAS”). This system uses a Draeger Alcotest device that some police departments use for PAS tests. However, the EPAS can be hooked up to a printer by hardline or blue tooth.

When Breath Tests Are Optional

The important thing to keep in mind is not whether you are being asked to take a breath test at the station or in the field, but whether you are pre-or post-arrest. Provided you are at least 21, and you are not on DUI probation, you can refuse a pre-arrest breath test without consequence.

Once you have actually been placed on arrest for DUI, however, you may not refuse a breath test unless:

• you have asked to take a blood test, and
• a blood test is available.⁵

3. Special Rules for Under-21 Drivers

Underage drivers can be charged with “standard” DUI:

• California Vehicle Code 23152(a) – driving under the influence, and/or
• California Vehicle Code 23152(b) – driving with a BAC of .08% or greater.

In addition, the California Vehicle Code has two special sections that punish drinking and driving by motorists under age 21:

• Vehicle Code 23136 VC — California’s “zero tolerance” law for underage drivers,⁶ and
• Vehicle Code 23140 VC — driving with a BAC of .05% or greater.⁷

Unlike standard DUI, violations of VC 23136 and/or 23140 may be established by either:

• a DUI chemical test or
• a PAS test.⁸

If you are under 21, a PAS test is not optional.⁹ If you refuse to take it after you are asked, you face suspension of your driver’s license for at least one year.¹⁰

4. Special Rules for DUI Probationers

Vehicle Code 23154(a) is California’s “zero tolerance” law for people previously convicted of DUI. If you are on DUI probation, you may not drive with any measurable alcohol in your system.¹¹

Violation of California Vehicle Code 23154 may be measured by either:

• a DUI chemical test or
• a PAS test.¹²

If you are on DUI probation, and you refuse to take a PAS test, you face suspension of your California driver’s license for one to three years.¹³

5. How do PAS tests measure BAC?

Most alcohol we consume gets absorbed in our stomach and small intestine. It then passes directly into the bloodstream and is carried to our organs.¹⁴

A small amount of alcohol, however, gets excreted into our lungs.¹⁵ It is this alcohol that is measured by breath testing devices.¹⁶

Unlike blood tests, however, breath tests do not directly measure BAC. A breath testing device must mathematically convert breath alcohol into a roughly equivalent BAC.¹⁷ For this reason, DUI breath tests are generally considered less reliable than DUI blood tests.¹⁸

Accuracy of PAS Test v. Post-Arrest Breath Test

Post-arrest DUI breath tests are governed by strict regulations relating to the training of breath testing operators and the maintenance of breath testing devices.

PAS tests are not, however, subject to these rules.¹⁹ As a result, they are even less reliable than post-arrest DUI breath tests.

This is just one more reason why you might want to think twice before agreeing to a PAS test if you:

• are 21 years or older and
• are not on DUI probation.

If you are at least 21, and you are not on DUI probation, we recommend that you politely refuse to take a preliminary breath test

Additional Resources

For more in-depth information, refer to these scholarly articles:

• Alcohol Breath Testing: Is There Reasonable Doubt – Syracuse Journal of Science and Technology.
• Comparison of breath-alcohol screening test results with venous blood alcohol concentration in suspected drunken drivers – Forensic Science International.
• Breath and Blood Alcohol Concentration Measurement in DUI Cases – Forensic Metrology.
• Measuring alcohol in blood and breath for forensic purposes-a historical review – Forensic Science Review.
• The Accuracy of Handheld Pre-Arrest Breath Test Instruments as a Predictor of the Evidential Breath Alcohol Test Results – Journal of Forensic Sciences.

Legal References