Blood alcohol in automobile drivers: measurement and interpretation for medicolegal purposes. I. Effect of time interval between incident and sample acquisition

The blood alcohol concentrations (BAC) were estimated by Breathalyzer at various intervals after drinking in 18 drivers, who estimated the time of their last drink; in 16 subjects who drank various alcoholic beverages; and in 11 subjects who drank various alcoholic beverages and then drove a car through an obstacle course. The ranges of Breathalyzer readings for the 3 groups were 0.08-0.20%, 0.06-0.13%, and 0.09-0.20%. Analysis of all the readings and comparison with expected values (calculated by using the known metabolic rate of alcohol) indicated that, when BACs of 0.06 to 0.20% have been reached by the time the test is made, and if the Breathalyzer reading is determined within 2 hr following a driving incident, the BAC is not practically different from what it was at the time of the incident because the rate of change during a 2-hr interval is less than the analytical error of the test procedure. The medicolegal implications are discussed.