A 2-Year Study of Δ 9-tetrahydrocannabinol Concentrations in Drivers Examining Driving and Field Sobriety Test Performance,
From November 1, 2010 through November 30, 2012, 1204 whole-blood samples were confirmed to contain THC alone or in combination with other drugs out of nearly 5000 Orange County, California, drivers suspected of driving under the influence of drugs. The goal of this study was to examine police reports and drug recognition expert evaluations of THC-positive samples within this 2-year time frame to determine whether there is a correlation between whole-blood THC concentrations and field sobriety tests performance on DRE and non-DRE evaluations. The FSTs prove to be sensitive to impairment by marijuana although as suspected, the findings of this study did not find a correlation between performance on field sobriety tests and the concentration of THC tested in whole-blood samples. Driving behaviors were also examined and found to be similar to those seen in alcohol impairment. Future studies examining DRE findings are needed to confirm the results.