Evaluation of breath alcohol measuring devices intended for evidential use in Victoria

The accuracy, precision and specificity for ethanol of eight different evidential breath alcohol measuring devices were evaluated. Other factors of importance, such as susceptibility to radio frequency interference and variation in the power supply voltage were also examined. On the basis of the above criteria, three instruments were identified as more suitable than the remainder for evidential use. These three instruments are based on the principle of absorption of infra-red radiation in the 9.5 um region and are the Drager Alcotest 7110, Siemens Alcomat V5.2F and Seres Ethylometre 679. Although the specificity of these instruments was adequate for most substances tested, it was not absolute. As a result, if these devices were introduced for evidential purposes, arguments may arise in the courts with respect to specificity of the devices for ethanol. Such arguments could not be resolved without recourse to physiological and toxicological data.