If someone is a murderer, he was on the scene at the time of the crime. Based on this, we can launch:. ['Zhang San was at the scene when the crime was committed, so Zhang San was a murderer.', 'Li Si was not a murderer, so Li Si was not at the scene.', 'Wang Wu was not present at the time of the incident, so Wang Wu was not a murderer.', 'Xu Liu is not on the scene, but Xu Liu is a murderer.']