Case 209
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.
Finley
“Either Reese or Parker is guilty.”
Drew
“Finley is innocent.”
Reese
“Either Drew or Taylor is guilty.”
Parker
“Finley and Drew are both innocent.”
Taylor
“Parker is innocent.”
Who is guilty?
Solution: Reese
If Reese is guilty, Reese's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.