Body temperature effects on breath testing

Most people are not aware that the breathalyzer utilizes a number of assumption. The machine has to perform a calculation to convert the amount of alcohol in a person's breath to the amount of alcohold in their blood.One of the assumptions is that a person's body temperature is a certain figure; it's an estimate, based on averages. As with any average, there will be some people who's temperature is different - some might be higher, while others might be lower. If the person's actual temperature is different from the average, it can impact the results - both higher and lower.

In Texas, that is usually something brought out on cross-examination of the technical supervisor. Apparently in Arizona that's not allowed. According to a recent article in the Arizona Star the Arizona Supreme ruled on Monday that defendants can present evidence that there are variables among invidviduals that make it impossible to come up with a precise reading.As you would the prosecutors are  not happy.

Arizona has a unique system, in which blood alcohol readings are extremely important - more important than simply determing guilt or innocence. If a person has a reading under .049 they are presumed to not be under the influence of alcohold. There's no presumption for a reading between .05 and .079. As in Texas, if the blood alcohol is .08 or over they are presumed legally intoxicated.

I don't know if Arizona prosecutes a lot of people who are under .08 - it soundls like they might. In Waco and McLennan County that seldom happens - unless the police believe the suspect is under the influence of some other substance. I suspect that's the same for most of Texas.

As with most decisions from other States, this decision has no impact on Texas Courts. It does point out however the necessity of having a lawyer who understands the science behind breath testing. If you don't know it, you can't challenge the results.

Walter Reaves
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Criminal Defense Attorney Walter Reaves has been practicing law for over 30 years.
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