Incorrect puzzle solution: the correct answer is A, B, C and D.
We know A and C are guilty, and it says "If D is innocent then B is innocent.", but we know that one of the criminals must be guilty. Therefore D is guilty. Another clue is "If C is innocent or D is guilty then B is guilty." Therefore B is guilty.
Incorrect puzzle solution: the correct answer is A, B, C and D.
We know A and C are guilty, and it says "If D is innocent then B is innocent.", but we know that one of the criminals must be guilty. Therefore D is guilty. Another clue is "If C is innocent or D is guilty then B is guilty." Therefore B is guilty.