To those from the outside looking in, Karl Bluestone looked like he had the perfect life. He was an honoured police officer, his wife a celebrated council officer, and a home full of children. But one day the veil slips and Karl Bluestone's true violent nature came to light with deadly consequences. Cops Who Kill lifts the lid on eight cases of murder and betrayal by police officers in Britain and around the world. In each episode, TV personality and actor Will Mellor is joined by experts, including ex-Detective Superintendent Julie McKay, psychologist Serena Simmons, and ex-Murder Detective Howard Groves, to try to unravel how and why a police officer switches from law enforcer to lawbreaker, how they were finally brought to justice, and the horrendous consequences for all concerned.