SJC on Cannabis Psychosis

In one of his final opinions before passing, Justice Gants delivered a win to defendants claiming an insanity defense where drugs were involved. But the decision’s implicit recognition of a connection between cannabis and psychosis raises concerns.

A new trial was awarded to an individual convicted of murder, who appeared to have schizophrenia. He was was also a heavy cannabis user experiencing withdrawal at the time of the killing. Certainly those who cannot control their own actions due to mental defect should not be treated as other criminals. A basic tenant of fairness requires that an individual know right from wrong before being criminally punished. To the extent that this decision shores up that principle, it is a good thing.

However, the implied recognition of a link between cannabis and psychosis is troubling. The scientific literature on this question is shaky at best. While there is evidence that cannabis withdrawal can affect mood, all-out psychosis is a claim often made but never proven. The worst example of this spurious theory making it into a courtroom, came at the trial of George Zimmerman for the killing of Trayvon Martin. The defense was allowed to argue that Martin’s marijuana intoxication somehow made him more of a threat to Zimmerman. The argument had racial overtones. The judge’s allowance of it, and the jury’s response to it, was likely grounded in outdated and unscientific beliefs about cannabis.

To be clear: No peer-reviewed scientific study has ever made a link between marijuana consumption and increased aggression. In fact, the only drug conclusively proven to cause aggression is alcohol. Alcohol remains legal and is almost never a basis for claiming insanity.

Though I am confident that it was not Justice Gants’s intention, one is now left to wonder whether police will use this decision to justify excessive force against cannabis users. Will police now claim that the smell of marijuana justifies pat-frisks and exit orders in the interest of officer safety? In legal terms, it should not lead to this outcome. But police officers read these decisions, and game them out for maximum power during citizen interactions. I expect to see more and more police reports identifying the presence of cannabis as a factor to justify intrusive interactions with citizens.