Cannabis and violent crime.

We present a series of 12 cases of violent crime, which were all committed under the influence of cannabis in Geneva, Switzerland, between 1996 and 2000. The crimes were committed by eleven males and one female, with a mean age of 26 years, who were using only cannabis at the time they acted. Most of them were chronic users. Five subjects had a past psychiatric history. Five had a personality disorder. Only three had been sentenced in the past for violent acts. At the time of the aggression, all of them exhibited adverse and acute effects of cannabis. All of them were judged by the court to be partially or totally non-responsible. Three cases are presented in more detail. Our data suggests that cannabis could have a specific role in the development of violent behaviour patterns and that detection of its adverse effects should be systematic in criminal responsibility evaluation.