Case 314
The Stolen Watch
A valuable watch disappeared during a private gathering.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Morgan
“Marley is innocent.”
Marley
“Neither Morgan nor Parker is guilty.”
Parker
“Morgan and Rowan are both innocent.”
Rowan
“Parker is innocent.”
Quinn
“Morgan is guilty.”
Who is guilty?
Solution: Quinn
If Quinn is guilty, Quinn's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.