Hazel Stewart, 49, was sentenced to life with no parole for at least 18 years for the two murders. She was present as Lord Justice Malachy Higgins told a courtroom packed with spectators the Court of Appeal saw "no reason to doubt the safety of this conviction," the Belfast Telegraph reported.
Stewart was only tried in 2011 for killing Constable Trevor Buchanan and Lesley Howell in 1991 after Dr. Colin Howell, a dentist and lay preacher, confessed the murders to church elders.
Buchanan and Lesley Howell, a nurse, were found dead from carbon monoxide in a car parked in Castlerock, a seaside town near Londonderry. Howell, a dentist, eventually pleaded guilty, saying he and Stewart, a former Sunday school teacher, conspired in the killing and made it look like suicide.
Stewart and Howell broke up about five years later.
Notable deaths of 2014 [PHOTOS]