Stan, what would be Reid Scale on the classic and controversial Bogle-Chandler deaths -- one even can't call them murders, quite, following certain - and also controversial - "revelations" of hydrogen sulfide as a possible causal factor back in '06 - in Sydney on New Year's morning back in 1963? I've long found this to be the classic Australian "unsolved" case and Taman Shud something of a non-starter.
(Anyone interested in this great, "has it all, practically," case should check out
http://www.boglechandler.com/ for the most complete account online, including coroner's inquest transcripts, and also see at
http://boglechandler.freeforums.net/ for discussion)