Circumstantial evidence
Emil Bessels (2 June 1847 – 30 March 1888) was a German zoologist, entomologist, physician, and Arctic researcher who is best known for his controversial role in the attempted but ill-fated "Polaris" expedition to the North Pole in 1871. Circumstantial evidence strongly points to Bessels as the most likely suspect in the death of the expedition's commander, American explorer Charles Francis Hall, by arsenic poisoning.