A study of blood alcohol stability in forensic antemortem blood samples

The effect of long-term storage on alcohol stability in preserved forensic antemortem blood samples was investigated. Thirty-two whole blood case samples (each with two tubes of blood) were used for this study. One tube from each case was analyzed for blood alcohol concentration (BAC) for court proceedings of driving under the influence (DUI), and all blood samples were then stored under refrigeration. After the storage time (ranging from 13 to 39 months) both tubes of blood for each case were reanalyzed for BAC and the results were compared to the original analysis. Seven samples originally negative for alcohol analysis remained negative. The comparative data for 25 samples demonstrated various losses in BAC in both tubes. A significant loss with a mean of 0.015 g/dL, was observed in previously opened tubes compared to a mean loss of 0.010 g/dL in unopened tubes. In order to determine the effect of other storage conditions, the same blood samples were then stored at room temperature for 6 months followed by 38 °C for 7 and 28 days and analyzed for BAC at the end of each storage time period. The seven alcohol negative cases remained negative when stored at room temperature or at 38 °C. Six months of storage at room temperature decreased BAC further for both tubes of the alcohol positive cases with a mean loss of 0.014 g/dL. Further storage at 38 °C for 7 days did not cause any significant change in BAC. Storage at 38 °C for 28 days caused some loss in BAC which was determined to be significant by statistical analysis.