A “Preliminary Breath Test” also called a “Portable Breath Test” or most often referred to as a PBT is a test a police officer may offer a person who he believes is an intoxicated driver. The DUI Detection and Standardized Field Sobriety Student Manual states: “The basic purpose of preliminary breath testing (PBT) is to demonstrate the association of alcohol with the observable evidence of the suspect’s impairment”. In other words, the PBT is to confirm that the officer’s observations, (poor balance, slurred speech) are a result of a chemical – – alcohol.
The results of a PBT are not admissible in court- – therefore, the Judge will never know the actual results of the PBT. However, some courts, (not all) will allow the officer to testify that he administered a PBT and based upon his “investigation” (including the PBT) he came to the conclusion that the individual was an intoxicated driver. There are courts that will not allow any discussion of the PBT- – not even a mention that one was given.
The reason the PBT result or in some cases even the mention of the PBT is not admissable is because it might detect residual mouth alcohol. As the Student Manual explains, “After a person takes a drink, some of the alcohol will remain in the mouth tissues. If the person exhales soon after drinking, the breath sample will pick up some of this left over mouth alcohol. In this case, the breath sample will contain an additional amount of alcohol and the test result will be higher than the true BAC (blood alcohol concentration)”.
As an Illinois DUI attorney for over 19 years, I find that if a person has submitted to a PBT it does not significantly harm his or her case.