The Demonstrated Linear Dynamic Range Challenge in PA DUI Breath Tests

“You gotta prove it before you can use it, and then prove it again.”

Would you use a pacemaker in a loved one if it wasn’t proven to work correctly before you used it?

Would you use a baby car seat with your child if it wasn’t proven to work correctly before you used it?

Would you use a pill to treat a loved one if it wasn’t proven to work correctly before you use it?

How about boarding a commercial airplane before it has been tested rigorously and found to be truly airworthy?

I would hope the answer to all of these would be a resounding “No.”

However, if you are a motorist accused of a DUI in Pennsylvania, that is exactly what the prosecutors are doing when it comes to evidentiary breath testing all across the Commonwealth of Pennsylvania.

They are not proving that the breath test machine works before they use it on people and prosecute them in a scientifically rigorous way, and they are not checking it in a scientifically acceptable way after they use it. There is a lack of true calibration of the machine, and a lack of true calibration checks.


As we have blogged before, there are plenty of issues in evidentiary breath testing.

The list of large systemic issues is perhaps bet summed up here: “Can someone honestly answer why there is still Breath testing for EtOH in America?

Other reports of acknowledged issues include:

Now we can add yet another breath testing challenge.

Our office (The McShane Firm, LLC) of Harrisburg, Pennsylvania filed a systematic challenge to the testing and calibration regime as it is currently practiced in the Commonwealth of Pennsylvania. We take no issue with the regulations but the implementation of those regulations.

It surrounds calibration and one very narrow, but significant aspect of calibration called the Demonstrated Linear Dynamic Range.

First some background:

To understand the concepts used and the important terminology, please visit:”Underage Drinking and DUI in Pennsylvania: LOD and LOQ Defense

An evidentiary breath test machine does not know how much it is measuring (the quantitative measure) straight out of the box when it comes from the vendor that sells it. It has to be “trained” or “taught.” This training of the machine as to how much is present is through the act of calibration (described below).

Quantitation (how much we have) is achieved through establishing a calibration curve. Without a demonstrated and proven calibration curve as to both the target analyte (EtOH), then you absolutely cannot quantitate validly. More on the importance and the nature of calibration curves can be read here: “When is a straight line a curve: Calibration curve

If proper quantitation has not been proven on the machine that your breath sample is run on, then this is good basic fundamental principles of science and analytical chemistry. So, they have not proven quantitation on the day and on the machine of the analysis of your breath. The absolute most any testing agency can scientifically say is that they are presuming so. They have no data to support the conclusion that on the day and time of the testing of your unknown and under the conditions that your test was run on that they can prove and show proper quantitation. Remember, there should be no presumptions in science. In the courtroom, by law, there is but one presumption. That is not that the laboratory could prove quantitation because they did so at some irrelevant time before or after on a different machine, but that of the presumption of innocence.

Some more information as to whether or not your particular case qualifies for the DLDRC can be found in this video below:

To see if your case or your client is impacted by this ruling, please call us at the McShane Firm, LLC today. Call 1-866-MCSHANE today.

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