Taimoor Rana is seasoned criminal defense attorney specializing in DUI related cases. He shares his expert legal opinion here « 10 DWI/DUI Myths and Their Facts – Part-3
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- Myth # 8:
Law enforcement officers can’t influence the BAC reading of a breath-testing machine.
Fact:
Law enforcement officers can and do influence BAC readings. Law professor and lawyer Lawrence Taylor quotes Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington. He said that, By far, the error which is most overlooked in breath testing for alcohol is the pattern of breathing…. During the breath the concentration of alcohol changes considerably… After discarding the dead space, the first part of the breath, has an alcohol concentration much lower than the equivalent BAC. Whereas, the alcohol concentration of the last part of the breath is much higher than the equivalent BAC. The last part of the breath could be over 50% above the alcohol level….Thus, it maybe indicated by a breath tester reading of 0.14% which has been taken from the last part of the breath that the blood level is only 0.09%.
It has been explained by Professor Taylor that, many police officers are aware of this error. They also know that if the machine opposes their judgment that the person they arrested is intoxicated, then it will effect their reputation.
So while taking the breath test they continuously ask the arrestee to keep breathing and breathe as harder as the person could. As found by Professor Hlastala, this is to make sure that the breath collected by the machine will be from the bottom of the lungs, near the alveolar sacs, where alcohol is in rich quantity. So it is a fact that with the higher alcohol concentration, the machine will give a higher but inaccurate reading.
Myth # 10:
The concentration of alcohol in a person’s blood stream (blood alcohol concentration or BAC) is measured by the Alcohol breath testers.
Fact:
This is not true as alcohol breath testers don’t actually measure BAC, because it can be measured only by analyzing a sample of blood. They just make an attempt to measure alcohol in the breath in order to make an estimation of the concentration of alcohol in the blood. Due to this reason their use is not permitted by all states.
As there is a 20-30 percent inherent margin of error in alcohol machines under ideal conditions, so it would be better to avoid being subjected to such an invalid device.
There are several good ways by which you can virtually eliminate being unfairly convicted of impaired or intoxicated driving by a BAC estimator. One is that you may quit drinking, another one is to slow down the rate of drinking and follow other tips for maintaining a low BAC, and another is to hire a designated driver.
What in actual happens is that, any chemical compounds that contain the methyl group in its molecular structure is detected by alcohol breath testers. Unluckily, there are thousands of such compounds. Many of them occur naturally in the human breath or they may be picked up from disease; inhaling fumes from gasoline, glue, paint, paint remover, new car smell, celluloid, cleaning fluids, etc.
We can assume that Breath testers are constants certain ratios within the human body that actually vary widely from person to person and also within the same person over time. For example, a 2,100-to-1 ratio is assumed by many breath-testing machines in converting alcohol in the breath to estimates of alcohol in the blood. Despite of the fact, this ratio varies from 1,900 to 2,400 among people and also within a person over time. This variation causes the false BAC readings.
A hematocrit (cell volume of blood) of 47% is assumed by some breath analysis machines. However, in men hematocrit values range from 42 to 52% and in women from 37 to 47%. A person who has a lower hematocrit will have a falsely high BAC reading. These machines treat female suspects differently. Alcohol breath machines are really BAC estimators.
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