The criminal is "C"
illustrator: kaoruIf "B" tells a lie, there comes to be 2 persons who tell a lie (B and A).
It contradicts the clues.
Therefore, "B" must be honest. At the same time, "A" must be honest, too.
And then, if "C" tells a lie, "D" tells the truth.
In that case, there comes to be 2 criminals (B and D). It contradicts the clues.
Therefore, only the one of lier is "D".
Then, "A","B","D" are not the criminal.
As a result, remaining "C" is the criminal!
"●Everyone
might tell a lie or tell the truth"
MISLEAD: you should ignore unreliable information