See also Melton v. State, 597 N.E.2d 359 (Ind. App. 1992), where an appellate court reversed a DUT conviction where evidence of BAG was presented to the jury based on a test performed on blood plasma. Expert testimony from the state was required to convert the reading into a whole-blood figure, the court said; tests on blood plasma samples register 18 to 20 percent higher than tests on whole-blood samples.
The fact is that laboratories often report blood test results as blood-alcohol concentrations when they are, in fact, serum-alcohol concentrations. And, as Frajola points out in his article, even where the laboratory does so by using a conversion ratio, they apply an average serum-to-blood ratio.
Unfortunately, the ratio of serum alcohol to whole-blood alcohol varies from one individual to another, just as the blood-breath partition ratio varies. The actual conversion factor in translating serum results to whole-blood results ranges from 0.88 to 1.59, with a median of 1.15. See Relation Between Serum and Whole-Blood Ethanol Concentrations, 39 Clinical Chemistry 2288 (1993). Yet laboratories usually use a uniform ratio of 1.16:1 in converting a serum/plasma BAG figure - if the figure is converted at all.
Defense attorneys confronted with a DUI case involving analysis performed on blood serum should definitely review an article entitled Blood Is Thicker Than Water: What You Need to Know to Challenge a Serum Blood Alcohol Result, appearing in the Fall 1993 issue of Criminal justice. Its authors, law professor Carol A. Roehrenbeck and attorney Raymond W. Russell, suggest that the following points be developed in challenging the blood test's admissibility and attacking its credibility before the jury:
Finally, DUI lawyers should be aware that although the general practice in non-medical cases is to analyze whole blood, the experts say that whole blood should never be used for blood-alcohol analysis: Plasma is the preferred method. The reason for this is that alcohol is not uniformly distributed among the cellular and noncellular components of blood. See, e.g., Dubowski, Absorption, Distribution and Elimination of Alcohol: Highway Safety Aspects, 10 Journal for Study of Alcohol Supplement 98 (1985).
Thus if plasma was analyzed, the defense attorney should question the computation of blood-alcohol concentration. If, on the other hand, whole blood was analyzed, the reasons why this procedure is disfavored should be brought out.
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