Ever wonder why people place such trust in the reading of a breath testing device? I do all of the time. Police, prosecutors, judges and the general public, unfortunately, do not.
We use the Intoxilyzer 5000 in Louisiana. It is manufactured by CMI, a company in Kentucky which creates these devices for law enforcement use. CMI’s published materials acknowledge an overall margin of error of approximately ten percent. Not bad, but what does that mean over all?
Breath testing itself involves compromise. What alcohol is on one’s breath is not determinative of impairment. What alcohol is in one’s blood is. We are not testing blood alcohol with the machine. We are testing a breath sample and making assumptions based on that sample. Those who use the test to convict you do not insist that this process is completely accurate. The exact term that is used for the process is “general expectation of equivalency”. Now there is a concept that you can sleep well on!
Scientists have argued for decades that the process itself has flaws – from the method of calculating a ratio of breath to blood formula to the fact that one sample alone is not enough. Yet, we still accept it. But we are accepting these results without looking further. We are all different aren’t we?
An average woman who ingests the exact same amount of alcohol as a man will produce a breath reading that exceeds the man’s by 5.6 percent. The lung capacity of an African-American male is approximately 3 percent smaller than a Caucasian. Because of the smaller capacity, an African-American tester must expel a greater fraction of his lung capacity, thus the results are inflated by a factor of 3 percent.
Do you think that law enforcement is taking this into consideration? Me either.
How about other issues? Body type, respiratory and gastro intestinal issues can all throw the results askew.
So, next time you hear about breath test results, consider if you would bank your freedom on the reliability of your cell phone, your car or your computer.
Didn’t think so.
It’s just a machine, just like those.