Portable Breath Testing Devices

Preliminary/Portable Breath Testing (PBT)

Many people who are investigated for an IL DUI will be asked to blow into a handheld machine on the side of the road. This machine is known alternatively as a Preliminary Breath Test, or Portable Breath Test, or simply as a PBT. Illinois DUI attorneys know the dangers these machines pose in convincing people that you were intoxicated even if you were not.

These machines typically function by measuring a chemical reaction of alcohol in a fuel cell. These fuel cell alcohol detectors are highly susceptible to a variety of factors that can cause them to produce incorrect BAC results. Things such as the temperature of the machine, the outside air temperature, when you last consumed alcohol, medical conditions, and many other factors will affect the validity of the PBT test results.

Generally, the police are not allowed to testify that a PBT gave a specific alcohol reading. Instead, they are typically allowed to testify that the PBT results indicated the presence of alcohol. Illinois courts do not recognize that the PBT machines are scientifically reliable beyond detecting the presence of alcohol.

You are not required under Illinois DUI law to blow into the PBT breath machine when you are being investigated for an IL DUI. Your refusal will not result in the suspension of your driver’s license. The PBT is essentially another form of the field sobriety tests.

If you are under investigation for an Illinois DUI you should ask to talk to an Illinois DUI attorney before answering any questions to performing any tests, including the PBT. If the police officer does not allow you to call our office then you should refuse to answer any more questions or perform any tests. Call our office before you ever answer police questions or take any kind of field sobriety tests or breath tests.


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