LAUSR

The previous studies on ethanol stability in antemortem blood samples stored under various conditions have shown that ethanol concentration decreases with storage. The feasibility of measuring a forensically meaningful blood ethanol concentration in antemortem blood samples stored refrigerated (~4°C) from 4-7 years after the blood draw was evaluated in this research. All blood samples were collected into two 10-ml gray top Vacutainer® tubes as part of police driving under the influence investigations. In 29 cases, blood in the tube originally analyzed was retested after 5-7 years of refrigerated storage. Blood in 41 cases was analyzed in a previously unopened blood tube from the case after 4-7 years of refrigerated storage. The first analysis of blood in each case occurred within 35 days of the blood draw. Initial blood ethanol concentrations ranged from 0.094 g/dl to 0.301 g/dl. No samples showed an increase in ethanol concentration with storage that exceeded the uncertainty of the initial measurement. All decreases in ethanol concentration were less than 0.020 g/dl. The mean differences in ethanol concentration in previously opened and unopened tubes were -0.014 g/dl and -0.010 g/dl, respectively. The results of this research support that antemortem blood in previously opened and unopened refrigerated blood tubes can be analyzed for ethanol content more than 4 years and as much as 7 years after the blood draw and provide a result consistent with the amount of ethanol loss expected from a test done within 1-3 years of the blood draw.