Case 246
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.
Riley
“Either Rowan or Blake is guilty.”
Rowan
“Either Riley or Blake is guilty.”
Reese
“Either Riley or Rowan is guilty.”
Blake
“Elliot is innocent.”
Elliot
“Riley is guilty.”
Who is guilty?
Solution: Riley
If Riley is guilty, Riley's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.