Clue by Clue: The Mystery Mugger Solution
The second suspect is lying. He said he saw someone running away with a superhero logo on the front of their shirt. He also said that he didn’t see the mugger’s face. That means he only saw the mugger’s back. So he didn’t see the front of the mugger’s T-shirt. He couldn’t know that the T-shirt had a superhero logo on the front or not.