Toxicological findings in fatal motor vehicle collisions in ontario, Canada: a one-year study.

Drug-impaired driving is a complex area of forensic toxicology due in part to limited data concerning the type of drugs involved and the concentrations detected. This study analyzed toxicological findings in drivers from fatal motor vehicle collisions (FMVCs) in Ontario, Canada, over a one-year period using a standardized protocol. Of the 229 cases included in the study, 56% were positive for alcohol and/or drugs. After alcohol, cannabis was the most frequently encountered substance (27%), followed by benzodiazepines (17%) and antidepressants (17%). There were differences in drugs detected by age but no marked difference in drugs detected between single and multiple FMVC's. Not all drugs detected were considered impairing either due to drug type, concentration or case history. The findings indicate the importance of comprehensive drug testing in FMVCs and highlight the need to consider a variety of factors, in addition to drug type and concentration, when assessing the role of drugs in driving impairment.