Medicolegal alcohol determination: variability of the blood- to breath-alcohol ratio and its effect on reported breath-alcohol concentrations.

There is substantial agreement among scientists that the variability of a person's blood- to breath-alcohol ratio contributes significantly to the experimental error in results from breath-alcohol analysis. Some have argued that the need to correct for this source of error can be eliminated by reporting breath test results in units of breath-alcohol concentration rather than blood-alcohol concentration. A simple mathematical proof is presented to demonstrate that this is not the case. Moreover, the scientific and legal flaws of this argument are discussed, and recommendations are offered for dealing with the problems that have developed from adoption of this view.