Despite earlier indications of poisoning, a British coroner ruled that a key witness in the Magnitsky fraud case in fact had died of natural causes.
https://www.nytimes.com/2018/12/19/world/europe/russian-whistle-blower-magnitsky.html
https://www.gazeta.ru/army/2018/12/18/12098947.shtml
https://echo.msk.ru/blog/oreh/2335521-echo/
https://www.gazeta.ru/social/2018/12/09/12088639.shtml
http://www.ng.ru/economics/2018-12-06/1_7457_answer.html