Case 091
The Missing File
A signed contract file vanished from the archive.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Harper
“Marley is guilty.”
Parker
“Marley and Emery are both innocent.”
Marley
“Neither Parker nor Emery is guilty.”
Emery
“Parker and Marley are both innocent.”
Lane
“Harper is guilty.”
Who is guilty?
Solution: Harper
If Harper is guilty, Harper's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.