Case 119
The Swapped Envelope
A sealed envelope was replaced with an empty one.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Taylor
“Neither Morgan nor Cameron is guilty.”
Morgan
“Either Blake or Drew is guilty.”
Blake
“Cameron is innocent.”
Drew
“Taylor is guilty.”
Cameron
“Blake is innocent.”
Who is guilty?
Solution: Drew
If Drew is guilty, Drew's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.