A large new study out of California reinforces the complete lack of evidence for our police forces’ current approach, which make no exception for prescription-carrying legal consumers of cannabis products. In this study nearly 200 adult males were randomised to smoke either active drug or placebo. THC and other cannabinoid concentrations in their blood, oral fluid (OF) and breath were measured at four time points. The subjects also completed driving simulations to test their SDLP (standard deviation of lateral position, i.e. ability to stay in their lane) and coherence (ability to follow another car). There was no correlation between either of the two driving ability measures and any of the blood, saliva or breath concentrations of cannabinoids. The researchers also had 11 California Highway Patrol officers, who were trained “drug recognition expert” (DRE) instructors, perform field sobriety tests (FSTs) on the subjects at four time points. If you’re thinking of this: Then yes, those tests. At the first time point, they correctly identified 81% of the active drug group as impaired. Unfortunately, they also identified 49% of the placebo group as impaired. Whoops. By the fourth FST around four hours after consumption, they identified as impaired only 23% of the active drug group, but still 13% of the placebo group. The authors write: “The complete lack of a relationship between the concentration of the centrally active component of cannabis in blood, OF, and breath is strong evidence against the use of per se laws for cannabis.”