The endgame of a tontine can naturally result in confusion, intrigue, and/or murder. This was a basis of the plots of several novels, most famously R.L. Stevenson’s The Wrong Box.
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That said, each Last Will & Testament creates the same scenario and (unlike in a Tontine) you typically know who you are in the Will alongside but this still doesn't seem to result in a spate of murder cases either.