Blood Alcohol Testing
DWI Defense Lawyer in Houston
The care of the blood sample once taken from the subject should be investigated.
It is a common practice to let the blood specimen sit for days before
analyzing it, due to delay in getting it to the laboratory, to a crowded
schedule in the laboratory, or to simple neglect. But blood is an organic
material and will decompose because of enzymes and bacterial action. One
of the results of this decomposition is that alcohol is created in the
blood. In a sample originally containing no alcohol, decomposition can
cause a reading of .25 percent or even higher, depending on the stage
of decay. Usually the specimen will be refrigerated to prevent this. However,
refrigeration will only slow down the decomposition process, not prevent
it. To stop this decaying of the blood and the resultant formation of
alcohol, a preservative such as a sodium fluoride solution should be added.
Failure to do this - and it is not at all uncommon - should provide defense
counsel with sufficient material at least to discredit the test results,
if not prevent their admission into evidence.
Most blood-alcohol kits used to collect blood samples for alcohol testing
use tubes containing 20 mg of sodium fluoride to preserve the blood sample.
The noted Swedish expert on blood-alcohol analysis, A. W. Jones, however,
claims that this is an insufficient amount to prevent fermentation: at
least 100 mg should be used.
Salting-Out Effect of Sodium Fluoride and its Influence on the Analysis
of Ethanol by Headspace Gas Chromatography, 18 Journal of Analytical Toxicology
292 (September 1994). Dr. Jones also found that using sodium fluoride to preserve a blood sample
actually increased the amount of alcohol in the sample when gas chromatography
was used to analyze it. According to his research, even 10 mg of sodium
fluoride "increased the concentration of ethanol in the equilibrated
(34 degrees centigrade) headspace by 8.9% when compared with heparinized
blood" (i.e., blood treated with an anticoagulant). This was due
to a "salting out" effect from the sodium fluoride.
Although many scientists believe that a preservative consisting of 1 percent
of the sample is sufficient to stop the growth of microorganisms, many
others feel that a 2 percent preservative such as sodium fluoride is required.
See Dick and Stone, Alcohol Loss Arising from Microbial Contamination of
Drivers' Blood Specimens, 34 Forensic Science International 17 (1987).
Clearly, the risk of fermentation will vary according to the amount of
preservative used. However, it will also be directly affected by the length
of time the sample is stored, and by the temperature at winch it is stored.
Sodium fluoride of 1 percent or less concentration is stable for only
about two days. Kaye,
The Collection and Handling of the Blood Alcohol Specimen, 74 American
journal of Clinical Pathology 743 (1980). And fluctuations from a storage temperature of 25 degrees centigrade
will increase fermentation and production of alcohol. As toxicologist
Anne ImObersteg of Park-Gilman Clinics in Burlingame, California, has observed:
Even in a blood tube containing sodium fluoride, Candida albicans, the
most common microbial culprit of ethanol production in blood samples,
can produce ethanol. See Blume,
Bacterial Contamination on BAC Stability, 60 American journal of Clinical
Pathology 700 (1973). Specimens stored at room temperature for more than five days showed significant
alcohol formation (up to 0.08 percent maximum) in a study by Chang arid Kollman,
The Effect of Temperature on the Formation of Ethyl Alcohol by Candida
Aihacans in the Blood, 34(1) JFSCA 105 (Jan. 1989). Therefore, the third prong of sample integrity, storage temperature,
is also crucial.
An anticoagulant such as potassium oxalate also should be added to the
sample to prevent the blood from coagulating. However, defense counsel
should insist that the prosecution establish exactly what chemicals were
used as an anticoagulant as well as the possible side effects on the alcohol
Cross-Examining the Evidence in Texas
Once counsel has obtained the laboratory records through discovery, they
should be reviewed for any notations concerning the condition of the blood
sample when received. Quite often, the lab technician will enter an annotation
such as "clotting" or "some coagulation." If so, this
should be developed during cross-examination - and the inference made
that if the anticoagulant was not working, then perhaps the preservative
was similarly ineffective (resulting in fermentation and an elevated blood-alcohol
Assuming that preservatives and anticoagulants were in the vial when the
blood sample was introduced, it should not be presumed that they were,
in fact, mixed with the blood. In
State v. Schwalk, 430 N.W.2d 319 (N.D. 1988), for example, the Supreme Court of North Dakota reversed a DUI conviction
where a foundation had not been laid showing that the collecting officer
mixed the blood and chemicals. The court refused to presume "compliance
with step four, which requires that immediately upon placing the blood
in the glass vial it must be inverted several times to dissolve the chemicals
contained in the vial."
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