Case 208
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.
Alex
“Taylor and Finley are both innocent.”
Jules
“Taylor is innocent.”
Taylor
“Alex and Finley are both innocent.”
Finley
“Either Alex or Morgan is guilty.”
Morgan
“Either Alex or Jules is guilty.”
Who is guilty?
Solution: Morgan
If Morgan is guilty, Morgan's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.