Sullum doesn’t buy the argument that drugs led to Michael Brown’s death:
One challenge for anyone pushing a pharmacological explanation of Brown’s alleged behavior: Despite speculation that he was on PCP, marijuana is the only drug that was detected in his blood. Kathi Alizadeh and Sheila Whirley, the assistant county prosecutors who presented evidence to the grand jury, did what they could with pot, raising the possibility that Brown had smoked enough to experience “paranoia,” “hallucinations,” and maybe even a “psychotic episode.” They planted that idea in jurors’ heads mainly by presenting a toxicologist’s misleading testimony about the amount of THC in Brown’s blood and the possible effects of large doses.
The toxicologist testified that Brown’s blood contained 12 nanograms of active THC per milliliter, a level that he said indicated Brown had consumed cannabis in the previous two or three hours. That contradicted testimony by Dorian Johnson, the friend who was with Brown when Wilson shot him. Johnson, who said he was with Brown all day, testified that they had planned to get high (hence the cigarillos that Brown stole from a convenience store) but never got around to it. Despite the blood test results, Johnson could be telling the truth. Daily marijuana users have been known to register 12 nanograms or more when they get up in the morning, and they may even perform competently on driving tests at that level.
German Lopez reviews the literature on pot and aggression:
While some research suggests marijuana users are more likely to be aggressive, multiple studies have found the connection between marijuana use and aggression fades away when controlling for other variables such as alcohol and hard drug use. Marijuana use, in other words, doesn’t appear to lead to more violence, and higher pot use doesn’t even correlate with more violence if other factors are taken into account.
A recent study on the topic, from researchers at the University of Tennessee in Knoxville, found that there’s no connection between domestic abuse and marijuana. The Knoxville researchers acknowledged that the issue needs more study, especially given the conflicting findings in previous studies. But the study shows that a link between pot and aggression is, at the very least, nowhere close to established.