Breathalyzer Test

Girl gives breathalyzer test for police officer.

The police officer asked you to take the breathalyzer and you cooperated. You might feel your chances at fighting this DWI is hopeless because the machine printed out a high BAC reading. But there are many flaws with the Intoxilyzer 9000, which the Austin Police Department uses at their station.

The police officer asked you to take the breathalyzer

1) Breathalyzers have a high false positive rate

Breathalyzers have a high false positive rate — especially if you still have alcohol in your mouth because this will create an artificially high BAC reading. A false positive rate is the number of people who are actually under the legal limit, but who blow into the breathalyzer and get a high reading that is over the legal limit. People who are actually under the legal limit who get arrested are treated the most unfairly by the system because they are arrested for something they didn’t do.

2) The machine could have overstated your blood alcohol level because of your lower-than-average breath to blood partition ratio.

Breath Alcohol Level is correlated to the Blood Alcohol Level, and the conversion factor is set at 2100:1, to convert breath alcohol reading to the blood alcohol level, which is the .08 legal limit.

The 2100:1 conversion factor, however, assumes that everyone who gets arrested for DWI has the same conversion factor. In other words, it doesn’t account for an individual’s own conversion factor, some may be as low as 1100:1 or higher than 2100:1.

For someone with an extremely low ratio of 1100:1, for example, use of the 2100:1 partition ratio would overstate blood-alcohol content on the breathalyzer test by double. Evidence showing a person charged with DWI had a low partition ratio could also show that they were not over the legal limit of .08.

3) The machine could have overstated your blood alcohol level because of your higher-than-average breath temperature.

Breath temperature is another area, like partition ratio, where the one-size-fits-all mentality is being used. The average temperature of exhaled human breath is 93.2°F. This number is an average. Your client might have had a breath test below, at, or above 93.2°F. Breath temperature is important because for every 1.8°F rise over 93.2°F, the breath test result is overestimated by 6.5%. Thus, if the subject’s breath test temperature is 98.6°F (the core body temperature), the breath test result is overestimated by 19.5%.

4) The breathalyzer test could have overstated your blood alcohol level because it detected non-alcohol molecules in your breath as more alcohol.

Furthermore, the Intoxilyzer 9000 is non-specific for alcohol. Any molecule that looks like alcohol under the machine is also detected as alcohol. This is especially problematic for people on low-carb diets, because they produce a disproportionately high amount of acetone in their breath, which looks like alcohol to the machine. Thus, if you have acetone in your breath as well, this will artificially inflate the breath alcohol reading to be higher than the actual breath alcohol level.

The verdict? The Intoxilyzer 9000 is a machine of many reasonable doubts we could convince a jury to consider leading to a not-guilty verdict.

If you gave a breath sample and want to discuss the specifics of your case, please don’t hesitate to give me a call at 512-898-9529 for a free case evaluation.

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