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Why failing a breath test may not lead to a conviction

On Behalf of | May 25, 2018 | Blog

As you make your way home, police officers stop your car. They clearly suspect you of driving while intoxicated, and eventually, they ask you to take a breath test. It shows a blood alcohol content of over 0.08 percent. Now what?

At this point, many people are ready to give up. After all, how can you argue with an objective chemical test? However, there are many reasons why breath test results may not be as bulletproof as people think.

The breath testing device is not working

In some cases, the breath testing device may not be functioning in a way that yields accurate results. Whether due to faulty software, defective parts or inadequate design, devices can fail, just like any other machine. This issue especially tends to arise when police departments use older models whose performance may degrade over time.

The officer did not operate the device properly

Even a properly functioning device need the right maintenance to keep running. Breath test device manufacturers provide instructions for regular calibration and maintenance that are necessary for accurate results. Especially when it comes to portable field units, officers may not always follow the prescribed routine. For example, neglecting to change the mouthpiece between stops can result in artificially higher readings.

Another substance affected the reading

Breath test devices work by measuring the alcohol percentage in the air you exhale from your lungs. Using a specific formula, it uses this percentage to extrapolate the BAC. There may exist several factors that could skew this ration.

If you retain alcohol in your mouth, you can get a reading that shows a high BAC, even though the alcohol is coming from right inside your mouth, not from air that has absorbed alcohol from your bloodstream. People with bridges and other types of dental work can retain small pockets of alcohol after a small drink that would normally not cause an elevated BAC.

Substances such as acetone can read as alcohol. If your clothing has acetone on it due to your work, this can happen to you. Some breath test devices also do not distinguish alcohol from ketones, which can be present due to diabetes or some low-carb diets.

The stop was not legal

Finally, if the police officers did not conduct the test based on a legal stop, the prosecution may not be able to use it as evidence. Officers making a DUI stop must have proper cause to believe you are committing or have just committed a crime.


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