Case 200
The Vanished Key
A locked evidence cabinet was opened without permission.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Jules
“Dakota is innocent.”
Alex
“Either Quinn or Logan is guilty.”
Quinn
“Either Jules or Alex is guilty.”
Dakota
“Jules and Quinn are both innocent.”
Logan
“Neither Jules nor Dakota is guilty.”
Who is guilty?
Solution: Alex
If Alex is guilty, Alex's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.