Law Offices of Michael Steven Sherman, P.C.

Science . Investigation . Preparation

We See What Other Lawyers Don'tSM

How Accurate are the Portable Breath Tests?

November 22, 2018

How Accurate are the Portable Breath Tests?Every testing device has its limitations. When you use cheaper devices, you normally compromise reliability and accuracy. This holds true when it comes to portable breath tests.

Police officers often use small handheld breath devices to test a driver’s blood alcohol content (BAC). Unfortunately, these devices have a number of issues which cause them to report inflated BAC levels.

Problem #1: Portable Breath Tests (PBTs) Measure Alcohol in the Breath, Not in the Blood

One major issue with breath testing is that it produces a blood alcohol content (BAC) reading when it is actually testing your breath. The machine uses a partition ratio to convert the alcohol measured in the breath sample to a BAC reading. This method is problematic because not everyone has the same partition ratio and thus the machine could report a reading that is higher than it should be.

Problem #2: Residual Mouth Alcohol

Another major issue with the PBTs the issue of “residual mouth alcohol”. This is the alcohol that is still in the mouth after a drink. Police officers are supposed to wait a certain amount of time before they administer the test to rule out any alcohol left in the mouth. Often times they do not. When this happens, the machine detects a high level of alcohol which is much higher than what is actually in your blood.

Issue #3: PBTS are not Specific to Alcohol

PBTs are not specific to alcohol. In fact, many common substances can trigger high readings. Some examples are paint thinner, nail polish remover, mouthwash, after shave, and hand sanitizer gels. If you used a substance like these and then took a breath test, it may cause an inaccurate BAC reading.

If you were recently arrested for a DUI and believe the PBT showed an incorrect reading, please call us now at 412-204-4138. Attorney Mike Sherman and his team know the scientific limitations of the breath testing machine and will work to challenge the evidence in your case. The consultation is free, so you have nothing to lose.

Share this Article


When faced with a serious criminal charge, it’s always important to have an experienced criminal defense attorney on your side. You need a DUI lawyer who can protect your rights, make sure you’re treated fairly, and who knows how to get results. Mike Sherman is that lawyer! Mike has over 30 years experience, including serving as an attorney with the Pennsylvania State Police for over 8 years. Mike knows both sides of PA DUI law!

Request your free telephone strategy session