A guy and his accomplice saw another guy running by himself and wanted to steal some money from the victim.
The two guys went up to the victim and stabbed him to take his money. What they didn't realize is that there was a witness nearby and that the knife would leave tool marks.
The police officer and the medical examiner are the specialists that arrived first at the crime scene. They used latent prints, DNA, trace evidence and physical evidence from the primary crime scene to find a suspect. Those were the key elements.
The Detectives had an interview with the witness and he said he could identify the guys if he saw them.
The detective had to examine a suspect. He said he had an alibi but they later found out he was lying.