A detective interrogates three suspects: X, Y, and Z. Exactly one of them is guilty. X claims: 'Y is the guilty one.' Y claims: 'I am innocent.' Z claims: 'X is lying about Y.' If only the guilty person is lying and the innocent people are telling the truth, who is guilty?
Y
Let's test Y as guilty. If Y is guilty, Y's statement ('I am innocent') is a lie, which fits the rule. X's statement ('Y is guilty') is true. Z's statement ('X is lying about Y') is false, making Z a liar too, which violates the rule (only one is guilty/lying). Let's re-evaluate: If X is guilty, X lies ('Y is guilty' is false). Y tells the truth ('I am innocent'). Z tells the truth ('X is lying'). This means X is the only liar and the only guilty person. Let's check: If X is guilty, X lies. Y is innocent, tells truth. Z tells truth because X lied. Therefore, X is guilty.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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