Cui bono

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Cui bono (/kw ˈbn/), literally "to whose benefit?", is a Latin phrase which is still used.[1]

It is the key forensic question in legal and police investigation to find who has a motive for a crime.

The phrase is a double dative construction. It is also rendered as cui prodest.

It is a Latin adage that is used either to suggest a hidden motive or to indicate that the party responsible for something may not be who it appears at first to be.[2]

Commonly the phrase is used to suggest that the person or people guilty of committing a crime may be found among those who have something to gain, chiefly with an eye toward financial gain. The party that benefits may not always be obvious or may have successfully diverted attention to a scapegoat, for example.

The Roman orator and statesman Marcus Tullius Cicero, in his speech Pro Roscio Amerino,[3] section 84, attributed the expression cui bono to the Roman consul and censor Lucius Cassius Longinus Ravilla:

Another example of Cicero using "cui bono" is in his defence of Milo, in the Pro Milone. He even makes a reference to Cassius: "let that maxim of Cassius apply".[4]

See also[edit]



  1. ^ Gerhart, Eugene C. (1998). Quote it completely, p. 258-259.
  2. ^ Adeleye, Gabriel G. et al. (1999). World dictionary of foreign expressions, p. 86.
  3. ^ Pro Roscio Amerino
  4. ^ Cicero, Pro Milone 32.3)