EMPLOYING SIMULATED DATA TO ILLUSTRATE AN IMPORTANT CAUSE OF THE STEEPLING EFFECT IN BREATH ALCOHOL ANALYSIS

The 'steepling' effect (large excursions in analytical data over time) is a debated issue in forensic breath alcohol analysis with various e xplanations being postulated. Simulated breath alcohol data was genera ted according to a hypothetical kinetic model where single random samp les as well as means of duplicate random samples were plotted with res pect to time at 0.2 hour intervals. In addition, the simulated data wa s compared when both two or more digit treatment was employed. Results showed the occurrence of significant noise or 'steepling' when single , two-digit breath alcohol samples were employed as compared to a four -digit mean computed from three-digit duplicates. The magnitude of var iability was quantified by means of nonlinear regression resulting in the residual sum of squares (RSS) = 0.00202 for the single analysis an d RSS = 0.00053 for the mean of duplicates. The method of data collect ion and treatment appears to contribute significantly to the 'steeplin g' phenomenon. Intuitively, replicate analyses reduce variability and allow for more accurate kinetic modelling employing breath alcohol ana lysis.