Case 082
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.
Sam
“Casey is guilty.”
Lane
“Either Sam or Casey is guilty.”
Emery
“Neither Lane nor Quinn is guilty.”
Casey
“Either Emery or Quinn is guilty.”
Quinn
“Sam and Emery are both innocent.”
Who is guilty?
Solution: Casey
If Casey is guilty, Casey's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.