Two expressed probabilities we're trying to disprove: 1: Other substances were involved 2: It was a LOT of marijuana Tough stats to find. From whitehousedrugpolicy.gov, I found the following: From 1991-1998, an average of 5.35% of all murders were drug related. Drug related is defined as those murders that occurred specifically during a narcotics felony, such as drug trafficking or manufacturing. In 1991, 3% of federal prisoners and 5% of state prisoners who had committed murder did so to obtain money to buy drugs. What is not delineated in these statistics are: 1: Of all drug related crimes, what percentage are marijuana related. 2: Of all marijuana related crimes, what amounts were involved. Nothing proven or disproven so far Next up, from a report from the USDOJ on marijuana in Washington DC: Direct correlation to other substances and increased violence in the DC area. However, here and here are actual news stories of murders over small quantities of marijuana. One in 2007 in the UK and one in 2008 in Toronto. I'm honestly not searching to support one side or the other. I can't find any definitive answers one way or the other. I do, however, somewhat resent the comment that those of us who made the conjectures listed are merely taking our thoughts from watching CSI. I would also like to point out that even for law enforcement officers, anecdote does not equate to evidence or data when trying to look at the bigger picture. My only conclusion is that marijuana related murder does happen in cases of both small and large quantities, but the ratio of those two cannot be determined. Finally, for those who support continued prohibition, check this out: