Police officers in Oklahoma and around the country use preliminary alcohol screening devices during traffic stops to determine whether or not drivers are operating their vehicles under the influence of alcohol. Officers may ask for a breath sample when they notice signs of intoxication or after a motorist has failed a standardized field sobriety test. The devices they use work in much the same way as the more elaborate breath-testing equipment found in police stations, but they are not as accurate or reliable. That is why prosecutors rarely use the results of roadside toxicology tests in court.

PAS devices are used after motorists have been taken into custody to establish probable cause to charge them with DUI. More rigorous tests are then conducted at law enforcement facilities to gather evidence that will be handed over to prosecutors. While prosecutors will rarely concern themselves with the results of roadside breath tests, defense attorneys may introduce them in court if their results differ significantly from subsequent tests performed using more sophisticated equipment.

Motorists can refuse to submit to a roadside breath test, but doing so usually violates implied consent laws and can have serious consequences. In Oklahoma, refusing to submit to a breath test will result in their licenses being revoked or cancelled. They may also be required to install an ignition interlock device in their vehicle.

Experienced criminal defense attorneys would likely advise drivers facing DUI charges to cooperate with police, remain silent and request a lawyer. Refusing to submit to a breath test will rarely deter police officers from making an arrest, and it is also unlikely to prevent them from gathering the evidence they seek. This is because the probable cause police officers must have to demand a roadside breath test will usually be sufficient to obtain a search warrant that compels compliance.