What is the purpose of a preliminary breath test (PBT) in a DWI investigation?

The purpose of a preliminary breath test (PBT) in a DWI investigation is primarily to provide a quick estimate of the driver's blood alcohol concentration (BAC). This tool allows law enforcement officers to make an initial assessment regarding possible impairment, which can be essential in determining the next steps in the investigation. The PBT is designed to be a screening tool; it provides an on-site assessment that helps officers decide whether further testing or investigation is necessary.

Unlike a formal breathalyzer test that follows arrest, which is used to confirm BAC with legal standards, the PBT is not definitive and does not stand alone as evidence of guilt. It is not conclusive enough to establish legal consequences or to serve as the sole basis for an arrest; rather, it informs officers whether there is sufficient evidence to justify further action, such as a full custody arrest and additional testing.

Therefore, the PBT is a crucial component of the DWI investigation process, making it an important tool for law enforcement in handling suspected cases of driving while intoxicated.