How accurate are PBT (preliminary breath tests)?


The term Preliminary Breath Test (PBT) refers to a portable device widely used by police officers to measure the breath alcohol level of a driver on roadside DUI stops. Its results are not considered particularly accurate, and are admissible in court for only a limited number of purposes as stated under:


  • In order to determine the validity of an arrest.
  • As evidence that the defendant’s breathe alcohol content was higher at the time of driving.
  • As evidence that the defendant’s breathe alcohol content was lower at the time of driving.


Now a day’s PBT’s are the most commonly used devices by law enforcement officers to check drunk driving on roads and highways to measure the BAC approximately by measuring the alcohol in a person's breath. These are portable hand held devices which are easy to handle and provide quick results. A breathalyzer consists of three parts, a mouthpiece, two glass vials containing chemical reaction mixture, and photocells to measure color change.


Breathalyzers come in many different types ranging from disposable screening testers to digital display breath alcohol monitors. But broadly they fall under three categories: Evidential Breath Testing Devices, Non-Evidential Portable Hand Held Devices (PBT), and Disposable Devices. Evidential Breath Testing Devices are expensive and requires maintenance, calibration, handling by certified professional, and their results are admissible in court. Whereas (PBT) Non-Evidential portable hand held devices are used for preliminary screening purposes only. These devices are less expensive and their results are not admissible in court.


The main drawback of breathalyzers is that they are sensitive to various substances in environment like gasoline, paint removers etc which can give erroneous BAC level. The breathalyzers are also sensitive to temperature which can result in altered results.


If a police officer has reasonable cause to believe that you may be intoxicated, the officer may request you to submit a preliminary breath test. The police officer can make an arrest based upon the results of a preliminary breath test analysis. Keeping in mind that the device may not show correct results and a police officer can initiate an arrest based on the device’s results, it is not advisable for you to submit to a PBT. It is only a civil infringement to refuse a preliminary breath test, with nominal fines but it is a misdemeanor for a commercial driver to refuse a PBT.


To sum it all up the use of a portable breath test (PBT) as part of pre-arrest evaluation by the police may not be accurate. Further a preliminary breath test instrument (PBT) is not a proper breathalyzer, as it does not meet the breathalyzer accuracy standards and it does not use infrared technology to determine a person’s blood alcohol content. That’s the reason why PBT results are legally inadmissible at any DUI trial. A (PBT) preliminary breath test is considered just a field sobriety evaluation and a refusal to submit to a PBT, like the other field sobriety tests, is also admissible.


Most drivers give in to submitting a PBT, thinking that failure to do so may result in a breathalyzer refusal and license suspension. This is not true, refusing to submit to a preliminary breath test (PBT) cannot be held against a DUI suspect.



By Richard Jacobs

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