The jury in the High Court at Palmerston North was told in detail of the horrific injuries Mr Waipouri suffered in a prolonged beating at the hands of Gilling and Ashley Arnopp in Mr Waipouri's Rangitikei Street flat on December 22, 2006.
Mr Waipouri's body was found with severe facial and neck injuries, broken ribs, various internal injuries, his ear was mutilated and there were bite marks on his nipples.
The tip of his penis had been "removed" and, despite a meticulous search of Mr Waipouri's flat and surrounding property, has never been found. When police arrived and arrested the pair at the blood- spattered scene, Arnopp had blood around his mouth and his saliva was later found on Mr Waipouri's nipples. Gilling's saliva was found on his stomach.
The jury was told the injury to Mr Waipouri's penis was inflicted after his death. But no explanation of what happened to the missing tissue has ever been given, mainly because the Crown did not need to account for it in order to prove its case.
Arnopp pleaded guilty to murdering Mr Waipouri toward the end of the Crown case when he stood trial with Gilling last December.
Gilling maintained his innocence, and the jury in that trial could not reach a verdict.
As the jury at his retrial considered its verdict last night, Mr Waipouri's ex-partner and friend of about 15 years, Phil Penwarden, said the cannibalistic aspect to the attack was hard to deal with.
"It's always been mentioned - it's a difficult issue for the family to cope with that. It's taken a huge toll," Mr Penwarden said.
"Just the level of hatred that Stan suffered. The charge was murder, but he was literally tortured and mutilated in such a fierce and hateful attack.
"This aspect of cannibalism, what's New Zealand doing bringing up these young people who are given licence for such sadistic acts? Animals don't even do that kind of thing to each other, only humans are capable of that."
Both Gilling, 18, and Arnopp, 21, endured similarly dysfunctional childhoods, but Arnopp's was particularly disturbing.
Neither man knew who his father was, and Arnopp's drug addict mother killed herself the day before his ninth birthday, just days after he and his half-sister had been placed in foster care. Arnopp's childhood was characterised by abuse and neglect, including at the hands of his stepfather.
He lived in at least 13 foster homes and attended at least as many schools, from which he was almost always expelled for bad behaviour. He became addicted to alcohol and solvents and lived a transient life, often on the streets.
At Arnopp's sentencing in February, Justice MacKenzie placed "considerable weight" on the psychiatric reports before him.
"While you are assessed as being aware of your actions, [the attack on Mr Waipouri] was assessed by one psychiatrist as likely to have involved 'a loss of control in an individual with unresolved trauma in a context of substance abuse'," the judge told Arnopp.
"This suggests that you were not fully aware of the level of brutality involved in your actions."
Arnopp was sentenced to life imprisonment with a non-parole period of 15 years.