How reliable is breath
testing in determining a person's blood alcohol level?
The answer to this question is
extremely long and the subject of great debate. Breath testing
is used by law enforcement personnel for its ease and
convenience, not its accuracy. Further discussion of this matter
may be found at FAQ4.
Reliability depends upon the
ability of the machine to accurately measure the presence of
breath alcohol. Breath alcohol supposedly reflects the level of
alcohol in a person's blood. Alcohol in the blood, of course,
produces a depressive effect upon the central nervous system,
leading to intoxication. However, even a perfectly functioning
Intoxilyzer 5000 (the breath machine Texas uses) has problems
producing reliable results as to intoxication.
A couple of simple facts
illustrate some deficiencies in the machine:
1) The machine strictly assumes
that your breath and blood have a direct ratio of 2100:1. That
means an equal amount of alcohol will be found in 2100 ml of
breath and 1 ml of blood from the same person. Human beings'
true ratios range from under 1000:1 to over 3000:1. The 2100:1
assumption helps some people and hurts others. Any given
person's result could be inaccurately skewed by as much as 50%,
depending on the person's true breath to blood ratio. The
problem of breath to blood ratios in and of itself is good
reason to cast serious doubt upon the reliability and accuracy
of breath testing, and no make or model of breath test machine
corrects the problem.
2) The machine also strictly
assumes your breath temperature to be 34 degrees Celsius, which
is about 93 degrees Fahrenheit. If your breath temperature is
higher than that, your test result will be higher than your true
level. The converse is also true. Newer machines can adjust for
this inaccuracy, but the machine Texas uses does not.
This website is not meant to be
exhaustive, so consult a qualified attorney for further
information to this broad question.
to FAQ List --->
are for people 21 years or older, do not involve enhancements,
are not exclusive, and are limited to Texas.
**This page is for
informational purposes ONLY and must not be relied upon as legal
advice because it is NOT a substitute for the advice of a qualified
attorney, nor does it establish an attorney-client
Not certified by the Texas
Board of Legal Specialization.