Case 255
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.
Taylor
“Neither Lane nor Emery is guilty.”
Lane
“Neither Taylor nor Emery is guilty.”
Finley
“Either Emery or Peyton is guilty.”
Emery
“Either Lane or Peyton is guilty.”
Peyton
“Either Taylor or Emery is guilty.”
Who is guilty?
Solution: Peyton
If Peyton is guilty, Peyton's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.