On Thu, 07 Feb 2008 14:42:18 -0600, Gig 601XL Builder wrote:

They are quite effective else all the DUI convictions would have been thrown out.

Wikipedia seems to indicate that breathalyzers are prone to significant
error. One might be smart to demand a blood test instead.

From Wikipedia:
Breath testers can be very sensitive to temperature, for example, and will
give false readings if not adjusted or recalibrated to account for ambient
or surrounding air temperatures. The temperature of the subject is also
very important.

Breathing pattern can also significantly affect breath test results. One
study found that the BAC readings of subjects decreased 11 to 14% after
running up one flight of stairs and 72¡V75% after doing so twice. Another
study found a 15% decrease in BAC readings after vigorous exercise or
hyperventilation. Hyperventilation for 20 seconds has been shown to lower
the reading by approximately 32%. On the other hand, holding your breath
for 30 seconds can increase the breath test result by about 28%.[citation
needed]

Some breath analysis machines assume a hematocrit (cell volume of blood) of
47%. However, hematocrit values range from 42 to 52% in men and from 37 to
47% in women. A person with a lower hematocrit will have a falsely high BAC
reading.

Failure of law enforcement officers to use the devices properly or of
administrators to have the machines properly maintained and re-calibrated
as required are particularly common sources of error. However, most states
have very strict guidelines regarding officer training and instrument
maintenance and calibration.

Research indicates that breath tests can vary at least 15% from actual
blood alcohol concentration. An estimated 23% of individuals tested will
have a BAC reading higher than their true BAC. Police in Victoria,
Australia use breathalyzers that give a recognized 20 per cent tolerance on
readings. Noel Ashby, former Victoria Police Assistant Commissioner
(Traffic & Transport) claims that this tolerance is to allow for different
body types.[2]

http://en.wikipedia.org/wiki/Breathalyzer

--
Dallas