Detective Chief Inspector Rob Griffin, from the East Midlands Major Crime Unit, has told ITV News Central Susan and Christopher Edwards displayed a heartless attitude from the moment they were arrested.
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Officers were called to an allotment off Prospect Drive in Shirebrook at around 10am on Sunday (26 January).
Stefan Pakeerah, 14, was lured to New Parks in Leicester and bludgeoned and stabbed to death by Warren Leblanc in 2004.
West Midlands Weather: Cold and showery through tonight and Tuesday