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A closer look at the accuracy of breath tests

On Behalf of | Feb 12, 2024 | Criminal Defense

Driving under the influence is a serious offense that can have significant legal consequences.

One of the common tools used by law enforcement to measure a driver’s blood alcohol concentration is the breath test. However, the accuracy of these tests is often a subject of debate and scrutiny.

Variability in breath test readings

DUI breath tests estimate BAC by measuring the amount of alcohol in a person’s breath. However, various factors can influence the accuracy of these readings. For instance, individual physiological differences, such as body temperature and metabolism, may lead to variations in results. Additionally, environmental factors like temperature and atmospheric pressure can affect the reliability of these tests.

Mouth alcohol contamination

Another factor that can impact the accuracy of DUI breath tests is the presence of mouth alcohol. Residual alcohol in the mouth, whether from recent consumption or other sources like mouthwash, can artificially elevate BAC readings. This is particularly relevant when the breath test assumes that the alcohol measured originates from the deep lung tissue, where it correlates with blood alcohol levels.

Calibration and maintenance

The accuracy of DUI breath tests relies heavily on the proper calibration and maintenance of the equipment. Failure to maintain and calibrate the equipment appropriately can compromise the validity of the test results and potentially lead to inaccurate readings. Recently, 27,000 people convicted of a DUI during an eight-year period will get a new trial or withdraw a plea due to improper calibration of a breath-test device.

By raising questions about the accuracy of the breath test results, individuals charged with a DUI may create doubt about the validity of the evidence against them.