Alcohol Involvement in Fatal Road Traffic Accidents: A Forensic Toxicological Study of Drivers, Passengers, Pedestrians, and Cyclists in an Urban African Setting

Abstract

Background: Alcohol intoxication is a well-established risk factor in road traffic accidents (RTAs), yet its role among non-driving road users such as pedestrians, passengers, and cyclists remains underexplored. Postmortem toxicological analysis, particularly of vitreous humour, provides a reliable means of assessing alcohol levels at the time of death, provided contamination by fermentative microorganisms is ruled out.
Objective: This study aimed to determine the presence and quantify levels of exogenous ethanol in the vitreous humour of deceased RTA victims. It also sought to analyze the distribution of alcohol intoxication across different road user categories, assess the impact of microbial contamination on toxicological results, and identify demographic patterns among alcohol-positive fatalities.
Methods: A total of 100 vitreous humour samples were collected from confirmed RTA fatalities during medico-legal autopsies. Each sample underwent microbiological screening to detect contamination with fermentative bacteria or fungi. Forty-two samples (41.6%) were excluded due to microbial growth, particularly with organisms like Candida albicans, Proteus spp., and Staphylococcus aureus, which can produce ethanol postmortem. The remaining 15 uncontaminated samples were analyzed for ethanol concentration and classified according to forensic toxicology thresholds into light, moderate, heavy, very heavy, and stuporous levels of intoxication.
Results: Ethanol levels ranged from 0.04 g% to 0.52 g%. Passengers accounted for the largest proportion of alcohol-positive cases (46.7%), followed by pedestrians (20%), cyclists (20%), and drivers (13.3%). Heavy to very heavy intoxication levels were found predominantly among passengers, while all intoxicated pedestrians exhibited stuporous levels (>0.35 g%). Young adult males (aged 21–40 years) were disproportionately affected. The findings also underscore the necessity of excluding contaminated samples, as postmortem microbial fermentation poses a significant risk of false-positive ethanol detection.