Case 219
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.
Parker
“Neither Kendall nor Logan is guilty.”
Kendall
“Parker is innocent.”
Logan
“Kendall and Alex are both innocent.”
Quinn
“Either Logan or Alex is guilty.”
Alex
“Logan is innocent.”
Who is guilty?
Solution: Quinn
If Quinn is guilty, Quinn's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.