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Factors That Can Affect Breath Test Device Accuracy

Anytime a Tennessee law enforcement officer stops you and believes you have been drinking, he or she will likely ask you to submit to a breath test conducted using with a breath testing device. The point of the breath test is to assess your degree of intoxication and determine whether you drank more alcohol before driving than the law allows, and, depending on its results, you may end up facing a driving under the influence charge.

If a DUI charge leads to a subsequent conviction, you can expect to face substantial penalties which may include jail time, steep fines, substance abuse treatment obligations and so on. Because so much is riding on the results of your breath test, it is critical that you have faith in the accuracy of its results. Breath test devices are not, however, foolproof, and there are a number of elements that affect the accuracy of the device. 

Electronic interference

It may sound strange, but electronic interference has the capacity to throw off the results of your breath test and cause it to produce a falsely elevated reading. Electronic interference can potentially come from any number of sources, among them cellphone towers, police scanners and radios, and so on.


Breath test devices are inherently sensitive to temperature, and if the person administering your breath test fails to consider the variations in your hematocrit, or cell blood volume, it can affect the results of your breath test. Both the temperature of the air and the temperature of the test subject can ultimately impact breath test results.

Poor calibration

A breath test device is a highly precise mechanism, and it must undergo regular calibration in order to produce accurate results. Improper calibration is one of the more common reasons people charged with DUIs seek to have their test results thrown out.

While these are some of the things that can impact the accuracy of a breath test, please recognize that this is not an exhaustive summary of all the factors that can impact test results.

The point to remember is that there are defenses to every DUI charge. If you are arrested, speak with an experienced DUI defense lawyer as soon as possible.