[authors: Clara Chan, Bruse Kelman, Nadia Moore and Allison Stock]
Commercial establishments where alcoholic beverages are served (e.g. bars, restaurants) and social hosts who serve alcohol in non-commercial settings may potentially be liable for damages, injuries and/or deaths caused by accidents alcohol-related involving people they served. Critical issues addressed by toxicologists often involve the interpretation and/or estimation of blood alcohol levels (BACs), associated clinical effects, and degrees of intoxication.
Alcohol consumption affects mental, cognitive, and physical functions in a dose-related manner (eg, greater consumption is associated with greater effects). Toxicologists combine blood alcohol levels with observed behavior to determine associated levels of impairment/intoxication.
It is generally accepted by toxicologists that the degree of physical and mental impairment from alcohol correlates with the blood alcohol level. In general, higher blood alcohol levels lead to increased impairment and higher degrees of intoxication. For example, typical effects of a blood alcohol level of 0.02% (or 0.02 g/dL) include some loss of judgment, decreased visual function, and divided attention. At a blood alcohol level of 0.08%, which is the current national limit for legally drunk driving in the United States, typical effects include poor reaction time, balance, speech, vision, hearing, perception, and judgment.
However, people who are chronic alcohol drinkers can develop a tolerance to the effects of alcohol and learn to compensate for their impairment. Alcohol tolerance means that alcohol has less of an effect, including on behavior, than in non-tolerant people. These individuals may not show obvious signs or symptoms of impairment even when their blood alcohol level is above the legal limit, even though they are in fact impaired. A person who consumes alcohol does not appear to be “drunk” simply because they have consumed alcohol. On the contrary, intoxicated behavior occurs when the amount of alcohol the person has consumed has exceeded the individual’s alcohol tolerance and produces mental, cognitive, or physical abnormalities. Whether an individual appears intoxicated depends on several factors other than alcohol consumption, including body weight, gender, race/ethnicity, amount of food consumed before drinking, drug or prescription drug use, and changes in social behavior learned over multiple drinking episodes.
When interpreting blood alcohol test results to determine the amount of alcohol consumed by an individual at a previous time, the toxicologist considers the quality of the sample taken and the analytical method used.
The “gold standard” collection of tissue samples for measuring blood alcohol content is a peripheral venous sample of blood or serum. Alternatively, a breathalyzer is a non-invasive method of obtaining an immediate result of an individual’s breath alcohol concentration. Interpretation of post-mortem specimens (i.e. collected after death) can be complex, as discussed later in this article. Forensic testing for BAC analyzes whole blood samples using gas chromatography (GC) methods, which provide accurate and selective quantitation of alcohol (i.e., alcohol). ethanol). In clinical settings (e.g., hospitals, emergency rooms), BAC is typically assessed in serum or plasma samples using enzymatic methodologies with lower precision but faster turnaround times (and cheaper). Due to differences in methodologies and types of biological samples analyzed, blood alcohol levels quantified in clinical settings using enzymatic methodologies are generally higher than the same samples quantified using medical GC assays. -legal. Toxicologists guide the interpretation of results taking into account the various factors of different tests.
The suitability of using BAC from post-mortem samples to reflect BAC levels before death (i.e. ante-mortem) can be complex due to redistribution after death. death and the potential for alcohol production related to decomposition. Each assessment to determine post-mortem sample adequacy (ie correlation with concentration at time of death) is unique. One approach is to compare the post-mortem BAC to alcohol concentrations measured in other biological fluid/tissue samples that are inherently less influenced by issues related to redistribution and decomposition (e.g., liquid vitreous humor of the eye, urine); the correlation between the different assessments increases the confidence that the post-mortem blood alcohol level accurately reflects the ante-mortem level.
An assessment of appropriate sample storage conditions may take place, as improper storage can alter samples such that alcohol levels may no longer reflect an individual’s blood alcohol level at the time of collection. For example, it is well known that the loss of alcohol from biological samples can result from evaporation and/or oxidation. Alcohol is volatile and evaporates from blood samples if sample containers are not properly sealed, resulting in loss of alcohol through evaporation. Alcohol loss can also result from the oxidation of alcohol (ethanol) to acetaldehyde in stored biological samples. Alcohol concentrations in biological specimens can increase when sterility is lost because alcohol (ethanol) production can occur as a by-product of biological growth. Under sterile conditions, the alcohol concentration in blood samples should not increase.
Toxicologists estimate the blood alcohol level of individuals based on the known pharmacokinetics of alcohol (i.e. the time and dose profile for how it is absorbed, distributed, metabolized and excreted) as well as specific attributes of the individual and of the consumption event under study. BAC assessments are generated to assess different parameters important to the problem being assessed, such as:
- Was the reported drinking pattern and timing (eg, what drinks were served and consumed and when) consistent with the measured BAC?
- How much alcohol would the individual have to consume to generate the measured BAC?
- Since the blood alcohol level was measured later, what was the person’s blood alcohol level when he left the service establishment and/or when the accident occurred?
- When assessing blood alcohol levels at the time of the accident (and if any), what was the contribution of the alcohol consumption of the service event under consideration compared to the additional alcohol consumed by the individual (either before arrival and/or after departure from the service establishment)? ?
The tool that toxicologists typically use for BAC extrapolations is the Widmark equation, named after the early 20e seminal work of the century led by Swedish physician, EMP Widmark. The equation uses a set of variables to mathematically describe the pharmacokinetics of alcohol in the human body. Specifically, the equation incorporates a uniform alcohol distribution (a one-compartment model) and a constant elimination/metabolism rate per unit time (zero-order elimination kinetics), as well as human factors specific (e.g., body weight and volume of distribution) and temporal variables (e.g., time elapsed since onset of alcohol consumption, time of crash and/or time of measurement blood alcohol level). The resulting equation describes the blood alcohol level as a function of an individual’s human factors as well as the time and amount of alcohol consumed. The precision of the estimates associated with Widmark’s equation depends on the reliability of the input parameters. Uncertainties arise with the number of assumptions made regarding an individual’s body weight, the type and alcohol content of beverages consumed, and the individual’s alcohol elimination/metabolism rate.
Host social liability issues are generally based on the alleged over-service of guests subsequently involved in incidents resulting in damage, injury, and/or death. The key issues in these questions depend on the amount of alcohol served by the establishment, the blood alcohol level resulting from the individual consumer, as well as the associated clinical effects and degree of intoxication.
As described in this article, JS Held toxicologists can address these and other issues, including sample validity and methodological assessments; extrapolations of BAC to earlier times; assessments to determine if the service profile (i.e. what and when) matches the measured BAC; and, if applicable, assessments to determine the alcohol contribution of the service event under consideration to the BAC at the time of the accident.
We would like to thank Clara Chan, MSc, DABT, Bruce Kelman, PhD, DABT, ATS, ERT, Nadia Moore, PhD, DABT, CIH, ERT and Allison Stock, PhD, MPH, MS for providing information and expertise that greatly aided this research.
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