He was given a sentence of 40 years in jail instead.
Blackfort Bill from Oro will have his jail term cut to 38 years after spending two of those years in custody.
Bill was convicted by the National Court on May 15 over the murder of his own uncle, Brenton Awai, on March 27, 2016, at Musa Block outside Port Moresby.
He brutally decapitated Awai while intoxicated.
The court described the killing as the worst in nature.