One of the tools that Oklahoma law
enforcement use to gather evidence of driving under the influence (DUI) is a
blood collection sample kit. This kit contains vacuum-sealed tubes, which are
designed to draw in a pre-determined amount of blood which then mixes with an
inorganic salt compound consisting of sodium fluoride and potassium oxalate.
Oklahoma blood test kits carry expiration
dates on the vacuum-sealed tubes. There may be some confusion as to the effect
these expiration dates may have if a police officer uses a tube that is beyond
its expiration.
The first question is whether the
expiration relates to the salt compound contained in the tube. The answer here
is, “no.” The compound itself is stable. This leads to the second, and more
significant inquiry: if the expiration date on the blood collection vacuum tube
does not refer to the salt compound, then what does it refer to?
The expiration refers to the tube
manufacturer’s warranty that the vacuum seal of the tube will maintain its
integrity to a degree sufficient to draw a pre-determined amount of blood. It
is the vacuum that draws the blood into the tube; but unlike the salt compound,
the tube seal eventually does degrade and as it does, the amount of blood that
it will draw into the tube becomes increasingly subject to uncontrolled
variation.
So what does this mean to you, if you are
subject to a blood draw using an expired vacuum tube?
The most significant impact of a loss of
vacuum is that the amount of blood drawn into the tube may affect the ratio
between the blood and the salt compound, which in turn may compromise the value
of the test result when it comes to establishing whether a driver was under the
influence when the blood sample was drawn. This potential volume-based skewing
of the test sample is referred to as, “salting out”.
A second possible problem with a loss of
vacuum integrity in the collection tube is that a compromised seal means that
more than the blood sample may possibly be able to enter it. Certain
commonly-found yeast bacteria, for example, may be able to enter via the
degraded seal. That bacteria consumes the blood sugar, or glucose, and as a
waste product produces… alcohol. That is correct: a contaminated sample due to
a faulty vacuum seal can result in the production of alcohol inside the tube.
What is more, there is no way for the
devices used to analyze the blood sample for alcohol content to distinguish
between the alcohol that was in your blood when the sample was drawn and any
bacterially-produced alcohol that was created after the draw. This can lead to
a challenge of the evidentiary value of the sample itself.
Are expired blood test kits being used in
Oklahoma? The answer appears to be, “Yes.” Documentation available from the state’s Board of Tests
for Alcohol and Blood Influence indicates that not only are some expired test
kits still in the field, but that the State Director of the Board of Tests has
given the green light to keep using them.
Not every blood draw sample in Oklahoma
will be subject to vacuum-seal compromise. And the state is encouraging law
enforcement in the state to turn in expired test kits. But if you have been accused of DUI based in part on the
result of a blood sample, the fact that some of these expired kits are
apparently still in use is an avenue that your attorney will definitely need to
investigate as part of your defense.
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