A serum blood alcohol test performed by a hospital is not the same measurement as the whole-blood alcohol concentration used in a Michigan DUI prosecution. The hospital ordinarily measures alcohol in serum or plasma for clinical treatment. The prosecution then seeks to translate that medical result into an “equivalent” whole-blood BAC.That translation is not a direct measurement. It is a second scientific estimate built on top of the first measurement. Unless the prosecution can establish the reliability of the hospital assay, justify the conversion method for the individual patient, and quantify the combined uncertainty of both steps, the converted number should not be admitted as reliable proof of a particular whole-blood alcohol concentration.
Short answer: A hospital serum result may show that ethanol was detected and may have clinical value. But it does not, by itself, establish the driver’s whole-blood BAC. A prosecution number produced by applying a population conversion factor must include a scientifically defensible uncertainty range that accounts for the hospital measurement and the conversion itself.
A Serum Blood Alcohol Test Answers a Different Question
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