Question: The murders commited by Colin Howell were the subject of an ITV drama series based on murders commited in what year?
Sentence (from "The Secret (TV series)"): The Secret is a 2016 Northern Irish ITV mini-series based on "Let This Be Our Secret", Belfast journalist Deric Henderson's account of the double murder of Lesley Howell and Constable Trevor Buchanan, whose bodies were discovered in a fume-filled car in the garage of a property in Castlerock, County Londonderry, in Northern Ireland in May 1991.
Relevant evidence: Yes