Agent John Hampton was an employee of the FBI. He had worked in the Phoenix field office before being transferred to New York City.
He was part of an undercover operation using the Aztec Club as a front. During this operation, he was a user of cocaine. He also provided it to actress Lilly Carlyle.
Hampton killed Wharton Carlyle, Lilly's father, to prevent his exposure of his drug activity and his undercover assignment. He framed Lilly's boyfriend Eddie Dutton, who had a double-edged switchblade, trying to replicate similar wounds in Wharton's body.
When Hampton was found out, he was presented Lilly's testimony against him to offer him a deal of confessing for a plea, partly to save the investigation. He smugly rejected it in believing his superiors wouldn't let him be arrested. In his horror, he was arrested by Major Case with his superiors relieving him of his testimony, failing in his pleas to be kept on the case to avoid legal penalties.
Hampton was found guilty of first-degree murder, conspiracy, obstruction of justice, false incrimination, and drug possession and distribution and was imprisoned. (CI: "The Insider")