What link?

I was reading a disturbing article about a murder trial in Australia. It seems that Australia's highest court found the man not guilty by reason of mental illness. Ok, that seems kosher, but get this. In the ruling they said that the man's mental illness was brought about by long term cannabis abuse. One of the justices had this to say, "This seems to be yet another example of the link between cannabis use and mental illness, a link which from my judicial experience and reading I regard as well-established." I would hope that instead of relying on judicial experience, they would rely upon well-established and scientific evidence, but I suppose this judges personal experiences outweighs medical science. According to the medical evidence that exists on marijuana, I don't believe any of it finds a link between cannabis use and violent behavior. If anyone out there disagrees, I would love to have the citations.