Preliminary Breath Test (PBT)

PBTs and passive alcohol sensors can greatly aid the identification and apprehension of hardcore offenders. Almost 20 percent of the police officers surveyed in a recent research study said PBTs are the best tool for identifying repeat offenders (Simpson and Robertson 2001).

The preliminary breath test (PBT) is the most common chemical test conducted in the field. A PBT device is a small alcohol sensor used by having the driver blow into a mouthpiece to establish his or her BAC. In most states, police must have reason to suspect the driver has been drinking before a breath test can be administered (Shults et al. 2001), unlike a passive alcohol sensor (see following section). The PBT results are then used to substantiate the officer’s opinion that the driver was impaired or intoxicated.

The devices are granted U.S. Department of Transportation approval if they meet accuracy and reliability standards. Generally, states allow PBTs to be used to provide evidence for an arrest but not to establish the driver’s BAC in court. PBTs are not necessarily as accurate as evidentiary breath testers because the field conditions under which they are used are less controlled.

Because many police departments have a limited number of PBTs, a majority of officers lack regular access to them.

“Officers in our survey estimate that over three-fourths of all DWI arrests result from routine patrol, so it is imperative that patrol officers have regular and consistent access to PBTs to assist with the detection of repeat DWI offenders during routine traffic stops” (Simpson and Robertson 2001).

PBT is only one component of detecting hardcore drunk drivers.

More experienced officers offer a note of caution with regard to the use of PBTs. In their experience, newer officers come to rely extensively on these test results. However, if the officer cannot establish reasonable grounds for applying the test, the results will be of no use in the prosecution of the case. It is still vital that newer officers be familiar with standard signs of intoxication and adept at conducting the SFST.

Preliminary breath tests are used in the following 36 states and Puerto Rico: Alaska, Arkansas, California, Colorado, Connecticut, Delaware, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Michigan, Minnesota, Missouri, Nebraska, Nevada, New Mexico, New Jersey, New York, North Carolina, North Dakota, Ohio, Pennsylvania, South Dakota, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming. Preliminary breath tests are used absent specific legislative authority, but based upon case law in Georgia, Maine and Wyoming.

Studies (Voas et al. 1997) have found the presence of a state law allowing use of PBTs was associated with a lower alcohol-related fatality rate. The distribution of PBTs to state and local police in Minnesota resulted in a substantial increase in the number of DWI arrests.

Shults, R.A., et al. 2001. Reviews of evidence regarding interventions to reduce alcohol-impaired driving. American Journal of Preventive Medicine 21(4S): 66–88.

Simpson, H.M., and Robertson, R.D. 2001. DWI System Improvements for Dealing with Hard Core Drinking Drivers: Enforcement. Ottawa, Ontario: Traffic Injury Research Foundation.

Voas, R.B., Holder, H.D., and Gruenewald, P.J. 1997. The effect of drinking and driving interventions on alcohol-involved traffic crashes within a comprehensive community trial. Addiction Supplement 2: S221–S236.