Case 282
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.
Noah
“Jordan is innocent.”
Kai
“Noah and Alex are both innocent.”
Jules
“Either Kai or Jordan is guilty.”
Jordan
“Either Noah or Jules is guilty.”
Alex
“Neither Kai nor Jordan is guilty.”
Who is guilty?
Solution: Jules
If Jules is guilty, Jules's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.