Case 260
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.
Blake
“Kai is guilty.”
Kai
“Either Blake or Jordan is guilty.”
Harper
“Either Kai or Jordan is guilty.”
Jordan
“Neither Harper nor Jules is guilty.”
Jules
“Neither Harper nor Jordan is guilty.”
Who is guilty?
Solution: Kai
If Kai is guilty, Kai's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.