Excessive drinking often plays a key role in fatal accidents. This makes measuring ethanol in post-mortem samples crucial in unnatural death cases. Studies in various countries find about 40-50% of unnatural deaths show high blood alcohol concentration (BAC) in post-mortem.
Forensic labs often set the BAC cut-off at 0.01 g% using headspace gas chromatography with flame ionization detection (HS-GC-FID) to analyse blood from both living and deceased individuals. This threshold suits driving under the influence (DUI) cases but poses issues for autopsy samples. Discovering an enlarged and fatty liver during autopsy suggests, though not specifically, that the person drank heavily. Liver inflammation or cirrhosis, confirmed through histology, indicates problematic drinking more precisely.
A major challenge in post-mortem BAC interpretation is ethanol possibly forming after death through microbial action and glucose fermentation in anaerobic conditions. Erik Widmark first raised this issue in his 1932 study on forensic alcohol. Elevated BAC is crucial evidence in determining responsibility in fatal accidents and police probes of unnatural deaths, given its link to impaired bodily functions.
Experts use the same methods to test ethanol in both the living and the dead. Yet, interpreting these results in autopsies is complex due to preanalytical factors. A major issue is the natural production of ethanol in decomposed bodies. This happens through microbial activity and blood glucose fermentation under anaerobic conditions. It’s important to tell apart ethanol consumed before death from that produced after.
One strategy is to test ethanol in other body fluids like bile, cerebrospinal fluid, vitreous humour, and urine. Comparing these with blood alcohol concentration (BAC) can help. Another method checks for alcohol biomarkers like ethyl glucuronide, ethyl sulphate, phosphatidyl ethanol, or serotonin metabolites (5-HTOL/5-HIAA) in urine.
To avoid post-death ethanol production, adding 1-2% sodium or potassium fluoride to post-mortem samples is essential. This stops enzymes from producing ethanol during shipping and storage.
Also, raising the BAC reporting threshold from 0.01 to 0.02 g% for PM blood might help. Since low BACs often result from post-death processes, especially in decomposed bodies, subtracting 0.05 g% from the average result could offer a clearer picture of pre-death alcohol consumption.
