David Benbow has filed an appeal against his murder conviction for killing his childhood friend, Michael McGrath.
McGrath was last seen in his Christchurch home in May 2017.
Two years later, former prison guard David Benbow was charged with his murder, accused of fatally shooting the 49-year-old.
But neither the gun, nor Mr McGrath's body, has been located.
A High Court jury found Benbow guilty of murder and he was serving a sentence of life in jail with a minimum non parole period of 17 years.
The Court of Appeal has confirmed he has filed an appeal against both his conviction and sentence.
A hearing date was yet to be set.