The Field Impairment Test (FIT) is used by UK police officers at the roadside. It aids the officer in the decision to arrest a driver stopped because of observed impairment of driving, and who, during the interaction with the officer, raised suspicion that drug use may be the cause. Under these conditions, the driver may be asked to perform the test, and if performance is unsatisfactory the officer may decide to arrest a driver on suspicion of driving while unfit through drugs. After such an arrest, enforcement procedures require the driver to be brought into a police station to be seen by a Forensic Medical Examiner (FME). If the FME certifies that the driver’s condition may be due to drink or drugs, a biological sample is obtained from the driver for drug analysis. This study was undertaken to assess the effectiveness of FIT. In part, this was achieved by assessing the level of concordance between police officers’ judgements at the roadside following the use of FIT and the results of drug analysis of biological samples obtained from drivers. In addition oral fluid was obtained on a voluntary basis from drivers who were released at the roadside following the use of FIT. The contribution of each component of FIT to the correct identification of drivers impaired by drugs was also assessed, and additionally, the nature and extent of drug use in this group of drivers was recorded. The performance of FIT as part of the police enforcement process was judged against an objective measure: the presence of drugs in the biological specimens (blood, urine or oral fluid) obtained from drivers who had been assessed by FIT. The majority of biological samples from those arrested were blood, and all specimens from those released at the roadside were oral fluid. While the mere presence of drugs in blood or oral fluid does not indicate impairment per se, the occurrence of toxicologically significant concentrations of drugs supports the presumption of impairment when supported by the officer’s record of impaired driving. The analysis in this study was based on information from a database set up to record the results of the FIT tests carried out by the 22 participating police forces and the results of laboratory analysis of biological specimens for cases proceeding under Section 4 of the Road Traffic Act. Additional information was obtained from supplementary forms completed during FIT by the officer and from analysis of oral fluid specimens voluntarily donated by the drivers who were stopped but not arrested at the roadside, and therefore assumed to be not impaired through drugs. In total, 991 appropriate cases were reported during the study period. Of these, 334 cases had the information required for the evaluation process (performance in FIT and the presence or absence of drugs in biological samples). For these cases the information was used to calculate the sensitivity (the proportion of true positive cases detected), specificity (the proportion of true negative cases detected) and accuracy (the proportion of cases that were correctly diagnosed in the study sample). The study results demonstrate that oral fluid can be used to identify drugs in drivers. Donation and collection of oral fluid specimens presented no operational hazard to police officers and was acceptable to drivers, including those who were drug positive. From the results obtained from the analysis of blood, urine and oral fluid, the nature and extent of drug use by drivers was found to be similar throughout the study areas, and reflected drugs misuse rather than the therapeutic usage of prescribed medicines. In relation to the use of FIT, the assessment of impairment by a police officer using the test was supported by the clinical examination performed by the FME in 77% of the cases. Biological samples were received and analysed in only 65% of this group but significant drug use was confirmed in 94% of them. Consequently, where there is initial suspicion of drug impaired driving supported by the use of FIT and the medical investigation, the procedure as a whole has demonstrated a high positive predictive value (94%). Overall, the roadside application of FIT demonstrated a sensitivity of 65%, a specificity of 77% and an accuracy of 66%, meaning that FIT identifies the majority of drug positive and drug negative cases. Consequently, FIT in its current form is useable for screening purposes. However, further development is required to improve its performance. The drug recognition skills of the police officers were generally good. Within the battery of tests that forms FIT, the pupillary examination contributed very little. Despite the positive results described above, there were several areas of concern. We were unable to obtain biological specimens from drivers where the FME did not corroborate the opinion of the arresting officer (23% of cases). From the significant number of drug positive cases found from the analysis of oral fluid provided by drivers released by the police officer prior to the involvement of the FME, there is concern that in these disputed cases there might be a high number of drug positives. Additionally, although we had only a small number of specimens volunteered at the roadside by those who were stopped but were judged to be unimpaired by the police officer, a significant number of these were drug positive (71%). This is of some concern as the majority of drugs detected in these specimens were indicative of drug misuse. This highlights the possibility that the current roadside procedure is not sensitive enough to detect all those impaired through drugs, or that there is a possible training issue for the police officer or that driver tolerance to the effects of the drug may explain this finding. Finally, there is no absolute definition of driving impairment nor is there an objective, validated method by which driving impairment (and FIT) can be assessed. (Author/publisher)
Samenvatting