Case 063
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.
Sam
“Either Kai or Noah is guilty.”
Casey
“Jules is innocent.”
Jules
“Either Sam or Casey is guilty.”
Kai
“Casey and Noah are both innocent.”
Noah
“Kai is innocent.”
Who is guilty?
Solution: Sam
If Sam is guilty, Sam's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.