He reportedly did have amphetamines in his system, and obviously that day was the first time that ever happened [sarcasm]. See previous post 'Drug addicts - get past the image, use logic'[LINK].
Would multiple taser hits carry an increased risk of death? Taser International and their distributors should know about such things, right? They wouldn't just make it up as they go along, would they? See [LINK]
For the correct answer, see [LINK].
Use of tasers carries a risk of death, even with healthy adults. [LINK]
Long duration or repeated tasers hits increase those risks. [LINK]
Those risks increase when the taser is used on the sorts of vulnerable people that it tends to be used on. [Common sense]
It shouldn't be such a great mystery when a vulnerable person is repeatedly tasered and dies.
The taser would leave no postmortem evidence.
The only real mystery is why we allow the stun gun salesmen to describe tasers as "safe", a la cigarettes 1960s.