Case 150
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.
Avery
“Either Frankie or Logan is guilty.”
Morgan
“Logan is innocent.”
Frankie
“Logan and Marley are both innocent.”
Logan
“Either Avery or Morgan is guilty.”
Marley
“Morgan and Logan are both innocent.”
Who is guilty?
Solution: Avery
If Avery is guilty, Avery's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.