Case 342
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.
Blake
“Harper and Finley are both innocent.”
Harper
“Neither Finley nor Logan is guilty.”
Finley
“Noah is guilty.”
Logan
“Finley is innocent.”
Noah
“Either Harper or Finley is guilty.”
Who is guilty?
Solution: Noah
If Noah is guilty, Noah's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.