What Is a Preliminary Alcohol Screening (PAS) Device?

When police pull you over on suspicion of driving under the influence (DUI), they can ask you to take a series of field sobriety tests. Their DUI investigation may involve observing basic motor skills, involuntary eye movements, and estimated blood-alcohol levels.

A law enforcement officer typically uses a preliminary alcohol screening device to estimate a suspect’s blood alcohol concentration. These hand-held devices aren’t considered accurate enough to be used as the basis for criminal charges. Instead, breath alcohol test results from PAS devices can help establish probable cause for an arrest.

This article discusses how the police use PAS devices. It also explains how a PAS device differs from the larger, more accurate tools often referred to by the brand name “Breathalyzer.”

You’ll need to understand the legal significance of a PAS device in your DUI case. A DUI defense attorney can review the evidence, including a breath test, and explain your potential next steps.

The Role of Breath Tests at a DUI Stop

A PAS device is a tool used by police to establish probable cause for a DUI arrest at the scene of a traffic stop. It is often confused with its larger, more precise cousin, the Breathalyzer.

Both are types of breath tests. Both indirectly determine the amount of alcohol in a person’s blood. Still, a blood test is the most accurate way of determining blood alcohol content.

How PAS Devices Work

The hand-held PAS device has a tube into which the suspect submits a breath sample. The device then provides an instant estimate of the suspect’s BAC.

Based on this estimate and other observations, the officer decides whether to make an arrest for being under the influence of alcohol. A positive preliminary alcohol screening test result isn’t necessary for an arrest. In many states, it’s also not admissible into evidence at trial for a DUI conviction.

Are PAS Devices Accurate?

In terms of accuracy, most states have determined that PAS devices aren’t reliable enough to be admissible as evidence. States have made this decision through case law or statute. PAS devices also aren’t subject to the same stringent police standards as BAC-testing instruments.

For example, Illinois statute (625 ILCS 5/11-501.5) explicitly states that roadside testing with a PAS device is only for determining probable cause. The law states that suspects can refuse the test.

But in Alaska, police can’t ask a motorist to submit to a preliminary BAC test unless probable cause has already been established.

Some states allow the defense to offer evidence from preliminary tests involving a PAS device. The evidence is admissible to show that testing was somehow defective or inaccurate.

PAS Devices vs. Breathalyzers

The larger, more accurate instruments used at the police station are subject to strict procedures and calibration standards. These instruments, known as Breathalyzers, have safeguards to prevent false positives. They’re generally considered quite accurate.

It’s difficult for a defense attorney to challenge the admissibility of the results of a Breathalyzer test. In contrast, PAS test results are excluded in many states because they don’t meet the high standards of reliability and accuracy.

The PAS device is one of several tools for determining whether a motorist should be arrested for a DUI. In contrast, the stationary breath screening instrument at the police station is used to establish a criminal case against a defendant.

Can I Refuse a PAS Test?

Under most state implied consent laws, you’re not required to submit a breath sample for analysis by a PAS device. Implied consent laws apply to the evidentiary BAC test taken after an arrest. There are exceptions.

Loss of driving privileges is a significant effect of many driving while intoxicated (DWI) convictions. For instance, in California, drivers under 21 can lose their driver’s license for one year if a PAS device shows a BAC of just 0.01%. Florida law is similar. It imposes 50 hours of public service (and license suspension until service is completed) for drivers under 21 who refuse to submit to a PAS test.

But suppose you decline to provide a breath sample during a roadside field sobriety test. If your case goes to trial, that fact can be used against you in court. This is true even if the test results are inadmissible. The jury can see a refusal to take a breath or chemical test as an attempt to evade arrest.

Ask an Attorney About Fighting a DUI

Getting pulled over in your motor vehicle and being arrested for a DUI is a stressful experience. You’ll want to avoid making any mistakes that could hurt your defense.

You have the right to a criminal defense or DUI defense attorney. Discuss the law and your rights, including the legal significance of a PAS device, with an experienced DUI attorney near you. A DUI lawyer can help educate you on DUI penalties, DUI probation, and DUI laws.