Case 298
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.
Casey
“Neither Noah nor Kendall is guilty.”
Noah
“Neither Casey nor Kendall is guilty.”
Dakota
“Noah and Kendall are both innocent.”
Kendall
“Noah is innocent.”
Emery
“Either Noah or Kendall is guilty.”
Who is guilty?
Solution: Emery
If Emery is guilty, Emery's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.