In the outwardly flawless life of Darren McKie and his wife Leanne, all seemed perfect. Residing in the affluent Cheshire, both Darren and Leanne enjoyed successful careers as police officers. Yet, beneath the surface, their seemingly ideal lifestyle concealed a web of deceit and mounting debts. 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.