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What Is The Portable Breath Test? What Is It’s Purpose?


A portable or preliminary breath test device, commonly referred to as a PBT, is a handheld machine that motorists are often asked to blow into on the side of the road. It is a screening device that is fraught with many pitfalls. Your Pennsylvania DUI attorney should know the dangers these devices pose when prosecutors use them to convince the Court that you were impaired.

Handheld machines to do not have safeguards or maintenance procedures like desktop models. They are prone to a high error rate. 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 errors that can cause them to produce incorrect BAC results. Things such as mouth alcohol, contamination, interfering substances, the temperature of the machine, the outside air temperature, when you last consumed alcohol, medical conditions such as acid reflux, lack of observation period, 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. Pennsylvania courts have ruled that PBT devices are scientifically unreliable beyond detecting the presence of alcohol. PBT results are never admissible at trial.

You are not required under Pennsylvania DUI law to blow into the PBT device when you are being investigated for a Pennsylvania DUI. Your refusal will not result in the suspension of your driver’s license. The PBT is essentially another form of field sobriety testing. It can only be used to establish probable cause for your arrest.

What Is The Difference Between A Preliminary Breath Test (PBT) and The Evidential Breathalyzer Test At The Police Station?

Both testing devices are subject to a high rate of error. An “evidential” breath test device is typically a larger desktop machine that is kept at the police station. The primary difference between a portable, handheld device and a desktop evidential system comes down to maintenance, trustworthiness, reliability, and software. As explained earlier, the PBT essentially has none of the safeguards in place like the evidential breath test device. While the PBT device is fuel cell driven (very slow), the newer desktop devices give readings while the subject is blowing into the device. One of the key differences is that desktop machines are set up to prevent mouth alcohol and other contaminants from getting into your system; no such protection is built into PBT devices.

Is The Preliminary Breath Test (PBT) Voluntary Or Mandatory In Pennsylvania?

Most police officers won’t tell you: you don’t have to blow into the PBT. It is strictly voluntary. There is no penalty for not blowing into the PBT at the request of a police officer.

What Happens If You Refuse The Preliminary Breath Test (PBT)?

Submitting to a PBT is purely voluntary. There are no penalties for refusing the PBT.

What Factors Can Influence The Reliability Of The PBT’s Accuracy And Result? 

As stated above, PBT devices are subject to high error rates because of the many things that can interfere with a portable device. Portable devices simply do not have the built-in protections like their desktop counterparts.

Is The Result Of The Preliminary Breath Test (PBT) Admissible In Court?

The results of portable breath test devices are usually admissible at preliminary hearings or pretrial hearings to show that the police had probable cause to arrest you for DUI. PBT results are not admissible at trial, or any guilt determining proceeding because the Pennsylvania Courts have ruled that PBT’s are inherently unreliable.

Science. Investigation. Preparation. At Mike Sherman Law, we see what other lawyers don’t! We are passionate about providing an aggressive defense where we leave no stone unturned when helping our clients. Do you have questions? Call us immediately for a free strategy session.

For more information on Portable Breath Tests In Pennsylvania, a free initial consultation is your next best step. Get the information and legal answers you are seeking by calling (412) 471-5000 today.

If you are facing a serious charge, don’t delay. Call now to set up your free consultation at

412-471-5000

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