Want to trick a breath machine into a low test result? Or make sure
that you're not causing a false high reading? Not that difficult, says
a law firm of San Diego DUI attorneys and lawyers: just control your
breathing.
The simple fact is that these breath machines which determine guilt or
innocence in DUI cases are not exactly the reliable devices that law
enforcement would have us believe. There are dozens of factors that can
cause false test results. An example of that unreliability is the
fact that the results will vary depending upon the breathing pattern of
the person being tested. This has been confirmed in a number of
scientific studies.
In one, for example, a group of men drank moderate doses of alcohol and
their blood-alcohol levels were then measured by gas chromatographic
analysis of their breath. The breathing techniques were then varied.
The results indicated that holding your breath for 30 seconds before
exhaling increased the blood-alcohol level by 15.7%. Hyperventilating
for 20 seconds immediately before the analyses of breath, on the other
hand, decreased the level by 10.6%. Keeping the mouth closed for five
minutes and using shallow nasal breathing resulted in increasing the
blood-alcohol level by 7.3%, and testing after a slow, 20-second
exhalation increased levels by 2%. ("How Breathing Techniques Can
Influence the Results of Breath-Alcohol Analyses", 22(4) Medical
Science and the Law 275.)
Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine
at the University of Washington has gone farther and concluded:
"By far, the most overlooked error in breath testing for alcohol is
the pattern of breathing... The concentration of alcohol changes
considerably during the breath... The first part of the breath, after
discarding the dead space, has an alcohol concentration much lower than
the equivalent BAC (blood-alcohol concentration). Whereas, the last
part of the breath has an alcohol concentration that is much higher
than the equivalent BAC. The last part of the breath can be over 50%
above the alcohol level... Thus, a breath tester reading of 0.14% taken
from the last part of the breath may indicate that the blood level is
only 0.09%." 9(6) The Champion 16 (1985).
Many police officers know this. They also know that if the machine
contradicts their judgement that the person they arrested is
intoxicated, they won’t look good. So when they tell the arrestee to
blow into the machine’s mouthpiece, they’ll yell at him, "Keep
breathing! Breathe harder! Harder!" As Professor Hlastala has found,
this ensures that the breath captured by the machine will be from the
bottom of the lungs, near the alveolar sacs, which will be richest in
alcohol. With the higher alcohol concentration, the machine will give a
higher -- but inaccurate -- reading.
Lawrence Taylor is the senior member of an AV-rated law firm of
San Diego DUI
lawyers practicing drunk driving defense exclusively.
