The Measurement of Breath Alcohol: The Laboratory Evaluation of Substantive Breath Test Equipment and the Report of an Operational Police Trial

Abstract

Immediately following the publication of the Blennerhassett report on Drinking and Driving, the Home Office set up a group of scientists at the Central Research Establishment to evaluate breath alcohol testing instruments currently available throughout the world. The instruments which passed the laboratory testing were then evaluated under field conditions. Between 1 December 1977 and 26 June 1978 twelve substantive breath alcohol testing instruments, (four Intoxilyzers, four Mk. IV G.C. Intoximeters and four Breathalyzers), were used by police officers at twelve police stations, geographically widely spaced throughout Great Britain. All three types of instrument were used, in turn, at each location to test motorists who had provided specimens for laboratory analysis under the provisions of the Road Traffic Act (RTA), 1972. 1776 motorists were invited to assist during the period of the trial. Of the 1516 (85%) who agreed to provide specimens of breath, 1336 provided specimens of blood for analysis, and 991 of these cases were considered suitable for scientific comparisons between the breath instrument results and the blood alcohol concentration (BAC) reported on the Certificate of Analysis from the Forensic Science Laboratory, issued under the Road Traffic Act (RTA), 1972. These comparisons are described in detail and are used to indicate the practicability of breath analysis being used to replace blood or urine analysis for alcohol. The performance and durability of the equipment is described.