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Failing the chemical breath test does not always mean conviction

If law enforcement officers stop you based on suspicion of OWI, they will likely want to administer a chemical breath test to see if your blood alcohol content exceeds the legal limit of 0.08 percent.

Many people assume that failing the breath test means the end of the road in an Indiana OWI case. They make the major mistake of giving up. In reality, there could be a number of factors that can call breath test results into question.

How chemical breath test devices work

These devices work by measuring the blood content in the breath you exhale. The basic principle is that the air in your lungs absorbs a particular percentage of the alcohol in your bloodstream.

Theoretically, there is assumed to be a constant ratio between the concentration in the breath and the concentration in the blood. However, while this may work for most people, some may have a different proportion of breath to blood concentration due to factors such as weight or body temperature. In such a case, the breath test measurements would not yield a reliable percentage for BAC.

Improper calibration and use can affect results

Even the most sophisticated and up-to-date breath test device will produce inaccuracies if not properly maintained and operated. Typically, they need regular calibration by qualified technicians. Officers in the field may also neglect to perform essential tasks such as replacing the mouthpiece between tests.

Mouth alcohol and ketones can produce false positives

The accuracy of breath test results rests on the assumption that any alcohol measured in your breath comes from the blood circulating through your lungs. But what if your breath contains alcohol from another source?

Alcohol that remains in your mouth even after a very small drink can yield a deceptively high reading. This situation becomes more likely if you have dentures, braces or other equipment that can trap little pools of alcohol. Some mouthwashes contain alcohol; if you used one shortly before the stop, it can also affect readings.

Some people suffer from medical conditions that generate ketones, which some breath test devices may read as alcohol. This can result from conditions such as diabetes or even just from following a very low-carb diet.

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