Reliability of BAC Tests: BAC Breath Test/Breathalyzer | Worgul, Sarna & Ness, Criminal Defense Attorneys
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Reliability of BAC Tests: BAC Breath Test/Breathalyzer

This is the second of a four-part series of blogs covering the reliability of BAC tests commonly used by law enforcement officers in Pennsylvania.

In this blog, we consider the reliability of blood alcohol concentration (BAC) breath tests. Additional BAC tests that will be considered in upcoming blogs are BAC blood tests and BAC urine tests. If you’ve submitted to any of these tests after a DUI stop, it’s important to contact an experienced Pittsburgh DUI attorney at Worgul, Sarna & Ness, Criminal Defense Attorneys, LLC.

Call us today at (412) 281-2146 for a free consultation of your case.

BAC Breath Test

BAC breath tests are the most common form of chemical testing used by law enforcement to estimate blood alcohol concentration. This test can involve the use of a preliminary breath tester (PBT) unit – which is a lightweight, portable breath analysis device that delivers a quick result in the field – and/or a breathalyzer machine back at the police station.

The test subject breathes into the breathalyzer device, exhaling air that consists of alcohol traces. Test results from a breathalyzer are often considered sufficiently accurate for admission as prosecution evidence in a DUI case. However, results from a PBT unit in the field are simply used to establish cause for additional, more accurate BAC testing.

Breathalyzer Reliability

A negative characteristic that affects the reliability of breathalyzer BAC tests is in relation to their failure to take into account the varying personal traits of individuals. These tests are commonly conducted by applying an average multiplier to the BAC output reading. This multiplier – which is based on Henry’s Law – is 2,100, and is referred to as a “partition ratio.” This reflects the fact that on average, the amount of alcohol in a person’s breath is assumed to be 1/2100th of the alcohol level in the same quantity of blood.

Additional Causes for Potential Inaccuracy

The Supreme Court of the United States has weighed in on this matter. State vs. Brayman consisted of expert testimony from a chemist who explained that this ratio has the potential to vary depending on the individual being tested. Therefore, an experienced Pennsylvania DUI attorney may question the reliability of your breathalyzer test results by challenging this traditional average partition ratio assumption.

BAC tests using a breathalyzer are subject to issues involving faulty equipment and human error. In order to ensure accurate results, these testing machines must receive proper calibration on a regular basis. As well, particular characteristics of the individual receiving a breathalyzer test can affect the results and provide a false reading. These include the presence of mouthwash or breath fresheners, body temperature, the ratio of blood cells to blood plasma, and particular aspects of person’s diet.

Additionally, if the mouthpiece of the machine is not changed after each breathalyzer test, or if the subject is not under observation by law enforcement for 20 minutes prior to the test (as required by law), the results of the test may be flawed and/or inadmissible.

Contact a Skilled Pennsylvania DUI Lawyer

BAC breath tests are not the most reliable form of testing to determine blood alcohol concentration. If you submitted to a breathalyzer test after a DUI stop, you may have strong grounds to fight against any DUI charges filed against you. At Worgul, Sarna & Ness, Criminal Defense Attorneys, LLC, we know how to challenge the results of your breathalyzer test with the goal of minimizing or eliminating the penalties you are facing.

Contact us today at (412) 281-2146 to begin the process of building your defense.

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