cui prodest en · NOUN
Etymology
From Latin.
Meanings
-
(uncountable) The rhetorical question "Who benefits?", as used to establish motive for a crime etc.
On the basis of cui prodest, the British and French might have helped kill Rasputin (to prevent him from persuading the Tsar to make peace with the Germans), but the presence of agents from both countries seems unlikely.
2016 November, Donald Rayfield, “The Monk behind the Myth”, in Literary Review: