Principles And Pitfalls in Alcohol Toxicity, Part 5

AlcoholThe problems with the forensic use of breathing instruments for alcohol determination are that the human being is not and cannot be compared with a standardized test solution. The biological variability from one subject to the next is just too significant to allow for a comparison to a single model.

Extrapolation from Breath Alcohol Testing to Blood Alcohol Levels

The extrapolation from breath alcohol content into blood alcohol content level at the time of accident or arrest is one of the most important steps in the forensic process. While the extrapolation process takes into account simple mathematical extrapolation, it is imperative to understand that in most cases the extrapolation of the amount of blood alcohol concentration to a time other than the time when the specimen of body fluid or breath was taken from the subject is applicable only to the average person in a normal physical condition and may not be relevant otherwise. Current research has shown that there are multiple variables such as blood breath ratio, absorption rates of alcohol, elimination rates of alcohol, and difference in total body water. Accurate and precise extrapolation of evidential breath test results back to the time of driving is not possible using the current available technology (1,2).

Measuring and Determining Impairment in Alcohol Cases

Alcohol abuse effects are commonly associated with brain process impairment. Alcohol affects the motor and cognitive performance. The effects of alcohol are not uniform, and impairment varies across different types of behavioral functions. Two areas of functioning that are sensitive to alcohol impairment and assessed in field sobriety tests, are those of speech and vestibular functioning.

1. Winek, Charles; Esposito, Francis “Blood Alcohol Concentrations: Factors Affecting Predictions” pgs. 34-61.
2. Karch, Steven B. Drug Abuse Handbook Steven B. Karch, editor. CRC Press 1997 pgs.1152

About Nachman Brautbar, M.D., F.A.C.P.

Experienced in internal medicine, toxicology, occupational medicine, alcohol, drugs, and nephrology, with a specialization in toxicology; evaluation, analysis & interpretation of urine drug/alcohol tests; drug/alcohol concentrations in the blood; findings in blood and urine samples; assessment of driving under the influence. His list of academic appointments includes Associate Professor of Pharmacology and Medicine, and Clinical Professor of Medicine at the University of Southern California, School of Medicine. Dr. Brautbar is a peer reviewer for the Department of Human Health Services, earlier Agency for Toxic Substances and Disease Registry (ATSDR). Dr. Brautbar has been on the faculty of the National Judicial College and has lectured to judges on the issue of scientific evidence. He has been a visiting professor at national and international scientific institutions and centers such as Yale, Harvard, Mayo Clinic, and NIH. Dr. Brautbar is a fellow of the Collegium Ramazzini. Dr. Brautbar has testified in the California State Senate and the United States Senate on toxic groundwater contamination.

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