Case 249
The Missing Ledger
A confidential ledger disappeared from the office.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Alex
“Neither Marley nor Peyton is guilty.”
Marley
“Alex and Lane are both innocent.”
Jules
“Lane is guilty.”
Peyton
“Either Alex or Jules is guilty.”
Lane
“Marley is innocent.”
Who is guilty?
Solution: Jules
If Jules is guilty, Jules's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.