If you are pulled over by the police for suspicion of driving under the influence (DUI), you will be asked to take a series of field sobriety tests, which may involve the observation of basic motor skills, involuntary eye movements, and estimated blood-alcohol concentration (BAC). The officer typically uses a preliminary alcohol screening (PAS) device to estimate the suspect's BAC, but these handheld devices are not considered accurate enough to be used as the basis for criminal charges. Rather, PAS device results can help establishe probable cause for an arrest.
The following information will help you understand how the PAS device is used, how it differs from the larger, more accurate instruments often referred to by the brand name "Breathalyzyer," and its legal significance in a DUI case.
PAS Devices: The Basics
Often confused with its larger, more-precise cousin the Breathalyzer (and similar instruments used for gathering evidence), the PAS device is just another tool used by police to establish probable cause at the scene of the traffic stop. The hand-held device has a tube into which the suspect submits a breath sample, providing an instant estimate of the individual's BAC. The officer then decides whether to make an arrest based on that and other observations, but a positive PAS test result is neither necessary for an arrest nor admitted into evidence for trial in many states.
Just how accurate are these devices? It depends on who you ask, but most states have determined through case law or statute that they are not reliable enough -- nor subject to the same stringent police standards as are evidentiary BAC-testing instruments -- to be admitted as evidence.
Illinois statute (625 ILCS 5/11-501.5), for example, explicitly states that roadside testing with a PAS device is only for determining probable cause and that suspects may refuse the test. In Alaska, police may not ask a motorist to submit to a preliminary BAC test unless probable cause has already been established (Guerre-Chaley v. State, 88 P.3d 539 (Alaska App. 2004)).
Some states, however, allow the defense to offer evidence from preliminary tests (using a PAS device) to show that testing was in some way defective or inaccurate, often in comparison to the evidentiary test results.
PAS Devices vs. Breathalyzers
The larger, more-accurate instruments used at the police station are subject to very strict procedures and calibration standards. Those instruments (or Breathalyzers, as they're often called) also have safeguards to prevent false-positives and are generally considered quite accurate. While it's difficult for a defense attorney to challenge the results of a Breathalyzer test, the results from PAS devices are excluded in many states because they don't meet these high standards of reliability and accuracy.
Therefore, the PAS device is one of several tools for determining whether a motorist should be arrested for a DUI, while the stationary breath screening instrument at the police station is used to establish a criminal case against the defendant.
PAS Devices and Implied Consent
You are not required to submit a breath sample for analysis by a PAS device under most state implied consent laws, which are applicable to the evidentiary BAC test taken after an arrest. But there are exceptions. In California, for instance, drivers who are under 21 can lose their license for a whole year if a PAS device shows a BAC of just 0.01 percent. Florida law is similar, imposing 50 hours of public service (and license suspension until service is completed) for drivers under 21 who refuse to submit to a PAS test.
However, the fact that you declined to provide a breath sample during a roadside field sobriety test can indeed be used against you in court if the case goes to trial, even if the result of such a test could not be admitted. Such a denial could be seen by the jury as an attempt to evade arrest, similar to gargling mouthwash immediately after a traffic stop.
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