Close Enough for Government Work
Information
courtesy of Lawrence Taylor - DUIblog
With
more than a little federal coercion, all states have now passed
laws making it a criminal offense to drive with .08% alcohol in
your blood. And most people suspected of violating that law are
given breath tests to determine their blood-alcohol concentration
(BAC). The breathalyzer will take a small sample of the suspect’s
breath and estimate how much alcohol is in it -- and, then, estimate
how much may be in the blood. And what that machine says is pretty
much the end of it. There will be no second tests. There will be
no cross-examination of the machine.
Are
these machines so reliable and accurate that we have permitted them
to become judge and jury?
Scientists
universally recognize an inherent error in breath analysis, generally
of plus or minus .01%. That means that if everything is working
perfectly (an unlikely scenario), a .13% breathalyzer test result
can be anywhere from .12% to .14%. This has been acknowledged by
courts across the country (see, for example, People v. Campos, 138
Cal.Rptr. 366 (California); Haynes v. Department of Public Safety,
865 P.2d 753 (Alaska); State v. Boehmer, 613 P.2d 916 (Hawaii),
recognizing an even larger .0165% inherent error).
What
does that tell us about the accuracy of these breathalyzers? Well,
let’s take a test result of .10%. Taking inherent error into
consideration -- and assuming the machine was working perfectly,
the officer administers the test correctly, and the suspect’s
physiology is normal and perfectly average -- the true BAC could
be anywhere from .09% to .11%. In other words, the true BAC can
be 10% in either direction -- or, put another way, anywhere within
a 20% margin of error.
These
machines have a 20% margin of error?
That’s
right. A person accused of driving with over .08% BAC can be convicted
by a machine which, if everything
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