Case 051
The Swapped Envelope
A sealed envelope was replaced with an empty one.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Rowan
“Finley and Emery are both innocent.”
Finley
“Rowan and Emery are both innocent.”
Cameron
“Either Emery or Alex is guilty.”
Emery
“Cameron is guilty.”
Alex
“Neither Rowan nor Emery is guilty.”
Who is guilty?
Solution: Cameron
If Cameron is guilty, Cameron's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.