The decriminalization of marijuana and propagation of marijuana prescribed for medical reasons have resulted in an increase in driving while under the influence of marijuana. Currently, the legal definition of marijuana driving impairment varies by state across the United States. Expert witnesses such as drug recognition experts and medical toxicologists are needed during a discovery to educate attorneys and during a testimony to educate judges and juries. These proceedings provide an overview of the US case law about driving impairment, the current status of the legal thresholds used in the courts for the admission of the medical toxicologist as an expert witness in marijuana driving and related cases, and provides an understanding of evolving issues surrounding the admissibility of their scientific opinion testimony.
Keywords: Analytical and forensic toxicology; Cannabinoids; Drugs of abuse; Expert testimony.