Case 133
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
“Avery is guilty.”
Reese
“Either Jules or Avery is guilty.”
Dakota
“Neither Jules nor Kendall is guilty.”
Avery
“Either Reese or Dakota is guilty.”
Kendall
“Jules and Dakota are both innocent.”
Who is guilty?
Solution: Avery
If Avery is guilty, Avery's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.