"They were powerful enough to kill her," McWilliam said.
He pointed out Poihipi kicked Parakuka in the face when she attempted to get up off the ground.
He described Poihipi's actions as deliberate, fired by his anger and jealousy. He outlined the "set of lies" the Crown claimed he told.
The first was that Parakuka told him she'd been beaten up by a group of girls, another version was he'd seen her having sex with another man.
"He said he went to get a knife to stab that man, we know that isn't correct."
McWilliam pointed out the jury had been read evidence from a couple who lived at the house where Poihipi claimed to have seen his partner having sex, this confirmed they'd been the only people home that night and that they did have sex.
He said the blows struck weren't accidental and were not struck in a sudden impulse. In Poihipi's first police interview he'd shown no remorse or regret, minimising the attack by claiming to have inflicted only four to five blows.
McWilliam urged the jury to disregard evidence from Poihipi's sister that they came from a home were violence was inflicted on their mother on a daily basis.
"Tragically this is simply a case of a man going to find his girlfriend after she disappeared and he has bashed her after an argument . . . He assaulted her in a way that anyone who had done what he did would have appreciated the likelihood of death."
However, Poihipi's lawyer, Roger Gowing, contended that when the 19-year-old inflicted the blunt force injuries on Parakuka, he didn't know what he had done was likely to kill her.
Gowing said Poihipi accepted he inflicted blunt force injuries to his partner in a sustained and frenetic attack but he didn't intend to kill her.
"He did not have actual appreciation that the injuries he inflicted were likely to cause her death . . . He told police he didn't know she was going to die."
Gowing told the jury the key to their deliberations was what knowledge Poihipi did have at the time of the attack.
"He lost his cool, he was out of control at the time he lashed out, that is obvious, intoxication was a factor but not an excuse."
He argued Poihipi had lost his ability to think clearly and rationally and dismissed the Crown's claim the family violence he had witnessed as a child would not have impacted him in some way.
"I say to you as a young person growing up in that house he developed an indifference to violence. He has seen his mother get up [after a beating] and carry on with her day."
Parakuka had not done that.
"This broken young man would have had no idea what he did was going to kill his partner - this is a case of manslaughter, not murder," he urged the jury.
Justice Ian Gault is to sum up the case at 2pm before the jury retires to consider its verdict.
