Case 190
The Stolen Prototype
A prototype vanished from a secured workroom.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Finley
“Riley and Frankie are both innocent.”
Riley
“Either Finley or Alex is guilty.”
Lane
“Neither Finley nor Frankie is guilty.”
Frankie
“Either Lane or Alex is guilty.”
Alex
“Either Finley or Lane is guilty.”
Who is guilty?
Solution: Alex
If Alex is guilty, Alex's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.