Interpretation of low postmortem concentrations of ethanol

Area of Science:

• Forensic Toxicology
• Postmortem Ethanol Analysis
• Clinical Chemistry

Background:

• Postmortem ethanol formation can lead to inaccurate interpretations of blood alcohol concentrations (BAC).
• Low BAC levels (<0.05 g/dL) are particularly susceptible to misinterpretation due to postmortem ethanol production.
• Analyzing alternative specimens like vitreous humor and urine can help differentiate ante-mortem ethanol from postmortem formation.

Purpose of the Study:

• To establish a reliable threshold for interpreting postmortem blood ethanol concentrations.
• To assess the utility of vitreous humor and urine ethanol levels in cases with low BAC.
• To differentiate ethanol resulting from consumption versus postmortem ethanol formation.

Main Methods:

• Retrospective analysis of 381 postmortem cases with BAC between 0.01-0.04 g/dL.
• Comparison of blood ethanol concentrations with simultaneous vitreous humor and urine ethanol levels.
• Evaluation of specimen consistency (positive/negative) between vitreous humor and urine.

Main Results:

• At BAC of 0.01 g/dL, 54% of cases showed positive vitreous/urine ethanol; this rose to 63% at 0.02 g/dL.
• Positive vitreous humor and/or urine ethanol was observed in 73% of cases at 0.03 g/dL BAC and 92% at 0.04 g/dL BAC.
• Consistent results between vitreous humor and urine were found in 90% of cases, supporting their reliability.

Conclusions:

• A BAC of 0.04 g/dL or higher likely indicates ethanol consumption, especially when supported by positive vitreous humor or urine ethanol.
• Vitreous humor and urine are valuable specimens for confirming or refuting postmortem ethanol formation.
• This study provides a quantitative basis for interpreting low postmortem BAC values in forensic investigations.