Uncertainty in Theoretical Calculations of Alcohol Concentration

Background The best way to assess the sobriety of a person is, of course, the direct analysis of blood sample collected at time of crime. But it is very often, that the driver that perpetrated the accident, escaped from the place of crime and the alcohol analysis is performed on blood samples taken several hours after he or she was involved in a motor vehicle accident or in some form of crime. In this situation a forensic scientists is sometimes asked to estimate the blood alcohol concentration (BAC) of the person at the time of the accident or crime. Such estimates have been called “retrograde extrapolations” or “back calculations”. They can also perform so-called “forward estimations” when a range of theoretical blood alcohol concentration values is computed as the result of drinking of a given amount of alcohol beverage. These calculations are performed usually in order to estimate a BAC at the time of an accident or crime when no blood specimen has been taken. In this case supposedly reliable information concerning the person’s alcohol intake prior to the event in question is usually available [1].