Urinalysis:
Unreliable for
Blood-Alcohol
Information
courtesy of Lawrence Taylor - DUIblog
In
many states, a suspect's blood-alcohol concentration can be determined
with urinalysis. This is consistently the least accurate of the
three available methods of analysis. The reasons for this are basically
two.
First,
the test is completely dependent on the subject voiding his bladder
and then waiting 20 minutes for fresh urine to be secreted into
the bladder for a more representative sample. And it is virtually
impossible for an individual to completely void his bladder: There
will usually be about 10cc of old urine left. This urine will combine
with approximately 20cc of fresh urine produced during the wait,
resulting in a sample that is one-third old urine -- a sample that
will contain alcohol from many hours before the subect was driving.
Second,
urine often contains a yeast called Candida albicans. This organism
has an interesting characteristic: it manufactures alcohol in the
urine (caused by the interaction with glucose). This "immaculate
conception" of alcohol in the bladder has been confirmed by
numerous scientific studies. See, for example, "Bladder Beer
-- A New Clinical Observation", 95 Transactions of the American
Clinical Climatological Association 34.
To
make things more interesting, Candida albicans is also unaffected
by preservatives added by the police to urine specimens. In other
words, alcohol will continue to be produced inside the evidence
vial for days until it is finally analyzed at the crime lab.
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