My wife studies this stuff in great detail. She is a bestselling author of crime and suspense novels. She has all kinds of books on how to kill people and cover up crimes. She says there are a whole lot of ways to cause (for example) a heart-attack and make it look natural. Not saying that's what happened here. Just sayin.
Jane Jamison died last year mysteriously. She was a editor/publisher of UNCOVERAGE.net