Abstract
The forensic toxicologist is challenged to provide scientific evidence to distinguish the source of ethanol (antemortem ingestion or microbial production) determined in the postmortem blood and to properly interpret the relevant blood alcohol concentration (BAC) results, in regard to ethanol levels at death and subsequent behavioral impairment of the person at the time of death. Higher alcohols (1-propanol, 1-butanol, isobutanol, 2-methyl-1-butanol (isoamyl-alcohol), and 3-methyl-2-butanol (amyl-alcohol)) are among the volatile compounds that are often detected in postmortem specimens and have been correlated with putrefaction and microbial activity. This brief review investigates the role of the higher alcohols as biomarkers of postmortem, microbial ethanol production, notably, regarding the modeling of postmortem ethanol production. Main conclusions of this contribution are, firstly, that the higher alcohols are qualitative and quantitative indicators of microbial ethanol production, and, secondly that the respective models of microbial ethanol production are tools offering additional data to interpret properly the origin of the ethanol concentrations measured in postmortem cases. More studies are needed to clarify current uncertainties about the origin of higher alcohols in postmortem specimens.
Highlights
Blood ethanol analysis is the most frequent test performed in a forensic toxicology laboratory, as part of the investigation process of death, accident, or crime
Our previous studies [33,34,35,36] agree with those who questioned the reliability of the ethanol/1-propanol ratio per se, since it was shown that different bacteria could produce different patterns of 1-propanol, and other alcohols, in variable concentrations depending on the growth conditions
It is reasonable to assume that the yields of neoformed ethanol in real cases would be within the respective range observed in laboratory cultures (15–100%), with the glucose levels and the microbe species being the main determinants of the final ethanol concentration and yield in each case
Summary
Blood ethanol analysis is the most frequent test performed in a forensic toxicology laboratory, as part of the investigation process of death, accident, or crime. It is the forensic toxicologist who is challenged to provide the relative, available scientific evidence on the ethanol levels at death and the subsequent behavioral impairment of the person at the time of death [2,3,5,6] Factors, such as the putrefaction state of the cadaver at autopsy, the clinical history of the deceased, the determination of glucose levels, the identification of microbes in the analyzed sample, and the evaluation of the discrepancies between ethanol concentration from various sampling sites and from different specimens, have been used to evaluate the origin of the measured ethanol, in the effort to achieve feasible accuracy in interpreting the postmortem ethanol analysis results [1,2,3,6]. Acetone could be a final product or an intermediate of the metabolism of carbohydrates and glycerol, or the catabolism of fatty acids (Table 1) This association of the microbial 1-propanol neoformation to glucose fermentative pathways and to the fermentation of other biochemical substrates could explain why this higher alcohol is the most abundant alcohol detected in the postmortem stage besides ethanol
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