Jean-Claude Lacote, 53, and Hilde Van Acker, 56, are convicted in Belgium
The pair, known as the Devil s Couple , murdered Briton Marcus Mitchell in 1996
Mitchell was shot in the head and neck after confronting Lacote over a scam
Lacote and Van Acker evaded justice for more than 20 years using fake names, during which time Lacote became a TV host in South Africa