Ethanol stability from 9 years of a blind quality control program in blood alcohol analysis.

This article focuses on a nine-year study of ethanol stability in antemortem blood samples conducted through a blind quality control (BQC) program at the Houston Forensic Science Center (HFSC). The program involved analyzing 1,228 BQC blood samples, both ethanol-positive and ethanol-negative, stored refrigerated and processed identically to authentic casework to assess the accuracy and reliability of blood alcohol concentration (BAC) results over extended storage times. Findings indicate a gradual but minor decrease in ethanol concentration over time, with average losses within HFSC's measurement uncertainty, supporting the reliability of BAC results even after long-term refrigerated storage; however, samples older than two years showed greater variability and are recommended to be discarded. All ethanol-negative samples remained negative throughout the study, and no correlation was found between ethanol loss and initial concentration. The BQC program provides a real-time, blinded assessment of forensic toxicology procedures, enhancing confidence in BAC results used in legal contexts.