Breathalyzer
Inaccuracy:
Post-Absorptive
Information
courtesy of Lawrence Taylor - DUIblog
I've
received considerable response to yesterday's post, "Breathalyzer
Inaccuracy: Testing During the Absorptive State", including
questions concerning the accuracy of breath machines after the absorptive
state.
Even
in the post-absorptive state -- that is, when the body has reached
a state of equilibrium, or uniform distribution of alcohol -- there
are numerous sources of error attributable entirely to physiological
factors. Simpson's research has found that breath tests are inherently
unreliable, indicating uncertainty levels of 15 to 27 percent. In
an article written shortly before the one cited yesterday, he noted:
Over
90% of this uncertainty is due to biological variables of the
subject, and at least 23% of subjects will have their actual blood
alcohol concentration overestimated. Manufacturers' specifications
for the accuracy and precision of these instruments are inconsistent
with the experimental values reported in the literature and I
recommend that an appropriate amount of uncertainty be reflected
in the results from these breath analyzers, especially when they
are used for law-enforcement purposes.
Simpson,
"Accuracy and Precision of Breath Alcohol Measurements for
Subjects in the Absorptive State", 33(2) Clinical Chemistry
261 (1987).
Another
noted expert, Professor Michael Hlastala, Professor of Physiology,
Biophysics and Medicine at the University of Washington's Medical
School, concludes:
Breath
testing, as currently used, is a very inaccurate method for measuring
BAC. Even if the breath testing instrument is working perfectly,
physiological variables prevent any reasonable accuracy...
Hlastala,
"Physiological Errors Associated with Alcohol Breath Testing",
9(6) The Champion 19 (1985).
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