Breathalyzer
Inaccuracy....
It Gets Worse
Information
courtesy of Lawrence Taylor - DUIblog
The
previous two posts on the physiological sources of inaccuracy in
breath alcohol analysis have apparently caused considerable interest...and
a number of queries.
Let
me be clear: Simpson is far from alone in his conclusions. Those
involved in forensic alcohol analysis will generally recognize that
the most recognized authorities in the field include Dubowski, Jones,
Simpson and Hlastala. In the posts I quoted supporting conclusions
from Dubowski and Hlastala; Jones has expressed somewhat similar
views. To quote further from Professor Dubowski on physiological
sources of error (as opposed to operator error or defects in
the design or function of the machine itself -- of which there are
many)
First,
not all blood and breath alcohol curves follow the Widmark pattern,
nor is the elimination phase linear. Second, alcohol absorption
is not always complete within 60 to 90 minutes as often claimed.
Third, the peak alcohol concentration cannot be validly predicted
or established in an individual instance without frequent and timely
measurement of alcohol concentrations. Fourth, it is not possible
to establish whether an individual is in the absorption or elimination
phase, or to establish the mean overall rate of alcohol elimination
from the blood or breath, from the results of two consecutive blood
or breath alcohol measurements, however timed. Fifth, significantly
large short-term fluctuations occur in some subjects and result
in marked positive and negative departures from the alcohol concentration
trend line. Sixth, short-term marked oscillation of the blood or
breath alcohol concentration can occur at various points on the
curve, resulting in repeated excursions of the alcohol concentration
above and below a given concetration within a few minutes or for
hours. Finally, no forensically valid forward or extrapolation of
blood or breath alcohol concentrations is ordinarily possible in
a given subject and occasion solely on the basis of time and individual
analysis results.
Dubowski,
"Absorption, Distribution and Elimination of Alcohol",
10 Journal of Studies on Alcohol, Suppl. 98 (1985).
|
