After becoming involved in a disagreement that turned physical, Cooper punching Mr Mills twice in the head, and then struck him in the head with his elbow. Mr Mills fell to the floor and died.
Cooper then wrapped Mr Mills in bed covering and placed him in a crawl space underneath the shed before he dug a shallow grave in front of the shed and buried Mr Mills several days later.
He then used Mr Mill's bank card to withdraw the dead man's benefit, and created a fictitious social media account through which he communicated with Mr Mills' friends and family to create the impression that he was alive and had moved to Wellington.
A year later Cooper exhumed the body and placed the skeletal remains, except for the skull, into a nearby wheelie bin. He smashed the skull into pieces with a hammer.
The skeleton was discovered six to eight months later by staff of a demolition company, after Cooper dumped the bin at an unoccupied property.
Cooper appealed against his sentence, on the grounds that the jail terms were manifestly excessive because the judge took starting points that were too high, did not give adequate discounts for good character, remorse, or to reflect the totality of the offending.
Court of Appeal Justices Lynton Stevens, Patricia Courtney and Graham Lang agreed that the starting point taken for both charges was was too high.
However they found there was no need for further adjustment on the other grounds for appeal.
As a result Cooper's previous sentences were quashed, and replaced with terms of three years, nine months' imprisonment for manslaughter, and three years, six months' imprisonment for perverting the course of justice, to be served cumulatively.
