Case 315
The Lost Access Card
A master access card was taken from the reception desk.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Reese
“Hayden and Peyton are both innocent.”
Marley
“Either Morgan or Hayden is guilty.”
Morgan
“Either Marley or Peyton is guilty.”
Hayden
“Marley is guilty.”
Peyton
“Either Marley or Morgan is guilty.”
Who is guilty?
Solution: Marley
If Marley is guilty, Marley's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.