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How a Preliminary Breath Test (PBT) Can Ruin Your DUI Defense

Most Virginia DUI arrests result when a police officer observess some traffic offense, such as speeding, running a red light or stop sign, or having a defective tail light or brake light. The officer may smell alcoholic beverages in the car or on the driver's breath, and then his focus shifts from a mere traffic stop to a DUI/DWI investigation.

Virginia police officers routinely ask persons whom they've stopped and suspect of being impaired by alcohol consumption to "prove you're okay to drive" by performing a preliminary breath test. Those who agree to take a preliminary breath test sometimes find themselves convicted of a DUI, although their refusal to perform the test may have resulted in their case being dropped for lack of probable cause to arrest.

The officer will tell the person if he refuses to take the test, that his refusal can't be used against him in court, and that even the result of the test can't be used against him in court. Believing this, many people agree to take the preliminary breath test (PBT) in the hope an arrest for DUI will not occur, or even if it does, it can't hurt them to do it. Neither of the above statements is completely true, and unless one asks, the officer need not point out that the preliminary breath test is voluntary. 

Because most DUI and DWI arrests occur without a warrant, the officer must have probable cause to believe that the person was operating a motor vehicle while either impaired by alcohol (or drugs, or both alcohol and drugs), or intoxicated. The preliminary breath test is one factor the officer may consider in determining that probable cause exists to arrest for DUI or DWI.

In fact, the PBT result can be the only factor to justify a DUI or DWI arrest. Virginia's preliminary breath test statute permits the officer to arrest a person if the results of the preliminary breath test indicate there is any alcohol in the person's blood.

Many times, an aggressive and experienced Virginia DUI/DWI attorney can obtain great results for his client by challenging the probable cause for the arrest, therefore preventing the admission into evidence of the proof necessary to sustain a conviction of the charge. While the PBT result cannot be used at the trial to prove the driver was drunk or impaired, at a preliminary hearing or a suprression hearing challenging probable cause, the test results can be admitted to justify the arrest itself, and therefore permit the admission of subsequent evidence obtained -- such as the breathalyzer test, or in rare instances, a blood test -- to prove impairment or intoxication. I therefore advise my clients not to take the preliminary breath test if asked.