Colin Howell was a highly respected dentist in Coleraine, County Londonderry, and a prominent elder in the local Baptist congregation. His public persona served as a profound facade for a pathologically narcissistic and manipulative personality. His criminal descent was catalyzed by an illicit affair with Hazel Stewart, the wife of his church associate, Trevor Buchanan.

The plan to eliminate their respective spouses was framed as a divine necessity within their twisted rationalization. Howell’s cold-bloodedness was evidenced by his prior practice sessions, where he drugged Stewart to test her responsiveness, refining his ability to maintain control over his targets.

Howell’s operational plan was chillingly precise. He constructed a custom-built carbon monoxide delivery system using a vacuum pipe, tape, and a garden hose connected to his Renault vehicle’s exhaust. He incapacitated his wife, Lesley, by administering sedatives via a juice drink before pumping lethal concentrations of gas into the room.

Following her death, he traveled to Trevor Buchanan’s residence. After a violent struggle in which he manually subdued the victim, he administered gas to Buchanan, then transported both bodies to a garage in Castlerock. He staged the scene by placing them in a car with the exhaust running, creating a tableau that satisfied the initial (and lazy) investigative conclusion of a double suicide pact.

• Spontaneous Disclosure: After 18 years, the convergence of a failed multi-million pound gold scam in the Philippines and the tragic death of his eldest son triggered a religious crisis. Howell turned himself in to the authorities in 2009.
• Systemic Investigative Failure: The subsequent Police Ombudsman report highlighted that the 1991 investigation ignored clear physical evidence—such as defensive wounds on Buchanan—simply because the “suicide” narrative aligned with their moral assumptions about the victims.