Can you solve this?
Have you ever watched an old school detective show? The detectives on the scene have done their due diligence, but are stumped about the case. Just then a guy in a beat up car drives up to the scene. He gets out of his car and flashes his credentials. "Who is this guy, Sergeant?" The hot shot detectives ask with obvious objection. "I invited him" replies the Sergeant. The seemingly out of place detective, walks through the crime scene. He asks funny questions the presiding detectives didn't think to ask and looks in places they didn't think to look.
As the end of the episode approaches, the quirky detective reveals a number of small details that the others missed. He reveals: who committed the crime, when they did it, and how. The culprit interjects, "but how could I do this when I can't even walk." He replies, "That would be true if you were telling the truth about your ability to walk. Tell me something. How does a man that can't walk have shoes that are worn out? I saw the bottom of your soles. All of your shoes show consistent wear from usage."