Christchurch schoolboy Hayden Miles tried to escape from his attacker before being dragged back, pinned to the ground and beaten to death, a court has heard.
The 15-year-old, who died after what was described as a "brutal and prolonged" attack, was later cut into 12 pieces with a band saw and buried in two graveyards and a suburban backyard.
Gavin John Gosnell, a 28-year-old unemployed man, denies murdering Hayden on the night of August 22, 2011.
The jury this afternoon heard from Nicolette Vaux-Phillips - Gosnell’s girlfriend at the time of the attack.
She says the three had been drinking at the Cashel St flat where she and Gosnell lived, before Hayden insulted her former boyfriend.
"Gavin was standing in the kitchen and then Hayden sort of stood up and said something to Gavin, so Gavin came up and punched him," she told the court.
“He started beating him up, he started kicking him and punching him - saying that he should have left and that he deserved it.”
Ms Vaux-Phillips said Hayden tried to escape his attacker, but couldn’t.
"Hayden was trying to get away, but Gavin dragged him back [...] he would just hit Hayden harder and laugh at him."
She said Gosnell pinned Hayden to the ground and was punching him in the face and head.
"Hayden was crying and begging me to help him."
His shoes soaking with blood from the attack, Gosnell later forced the boy into a shower to "clean up", before leaving him on a sofa in the lounge.
Ms Vaux-Phillips said she heard Hayden moaning and making "funny noises" before she went to sleep. In the morning, she checked for a pulse and found him dead.
After discussing the matter with a friend, Gosnell decided to get rid of Hayden’s body, Ms Vaux-Phillips told the court.
She said Gosnell turned the volume of a radio up inside the house to mask noise and proceeded to dismember Hayden’s body with a knife.
He then used a saw to cut the body up in the living room. Ms Vaux-Phillips said she moved into the bedroom, but Gosnell came in with pieces of the body and was laughing about it.
She told the court when she returned to the living room, there was "blood everywhere".
"He told me that if I didn’t help him, or if I spoke to anyone about it, the same thing that happened to Hayden would happen to me.
"We went to a cemetery and there was two graves that were fresh, so Gavin said that was where he was going to put Hayden."
The remains were found by police four months later.
Gosnell’s defence counsel admitted the attack in his opening statement this morning, but argued it was a case of manslaughter and not murder.
“There is no doubt at all that Gosnell assaulted Miles… and that those injuries ultimately lead to his death,” he said. “The real question is – was it manslaughter or murder?”
A jury of six men and six women were allotted for the trial. It has been set down for three weeks.
Ms Vaux-Phillips was charged as an accessory to the murder last year but pleaded guilty when the charge was downgraded to culpable homicide. She was sentenced to one year home detention last May.