This retrospective study evaluates two distributions (n.968): Differences between preliminary breath test (pbt) results and the first evidential breath test (pbt-brac1) and differences between two (duplicate) evidential breath alcohol tests (brac1-brac2). The two distributions were shown to vary from each other and from the normal with statistical significance (p < .05). The pbt-brac1 distribution hadgreater variability (sd . .025) Than the brac1-brac2 distribution (sd . .010). The conclusion is that differences between roadside and subsequent evidential breath results cannot be attributed solely to absorption or elimination kinetics. Intra-individual breath sample differences can be large and thus obscure the accurate evaluation of absorption and elimination rates. Breath tests conducted within approximately 2 hours of driving will reflect, within experimental uncertainty, the brac at the time of driving.
Abstract