Case 236
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.
Noah
“Hayden is guilty.”
Taylor
“Either Noah or Kendall is guilty.”
Marley
“Taylor and Hayden are both innocent.”
Hayden
“Neither Taylor nor Kendall is guilty.”
Kendall
“Neither Marley nor Hayden is guilty.”
Who is guilty?
Solution: Noah
If Noah is guilty, Noah's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.