From what I've read he had two joints worth of cannabiniods in his bloodstream and if that killed him he's the first in 5000 years of use.

Some light reading...

http://www.norml.org.nz/article383.html

http://www.scoop.co.nz/mason/stories/PO0401/S00065.htm

http://www.nzdf.org.nz/update/messages/2372.htm