Edmonds and the woman had previously lived together in west Auckland with her two sons, aged 7 and 11 at the time of Mr Bettink's death, for around two years. But in early 2014 they separated, with Edmonds moving to Whanganui.
However, Ms McClintock said it was clear the relationship was not over in Edmonds' eyes. He continued to pay money into one of her son's bank accounts, and kept up a stream of texts and calls, which the woman responded to a "limited extent".
In the 46 days leading up to the alleged murder, Edmonds phoned and text the woman more than 200 times, which she responded to on "fewer and fewer" occasions, Ms McClintock said.
Mr Bettink was living with the woman by this stage, and on the morning of November 6 the Crown says Edmonds tried to phone the woman numerous times, without success. Suspecting she was seeing another man, he then called her friend, who said the woman had been driving a new car recently.
Edmonds then walked off his labouring job, got into his truck and drove the six hour journey to Auckland.
He got to the woman's house to find Mr Bettink there looking after her sons while she was out collecting a takeaway dinner.
The two men had coffee and it became clear they both believed they were the woman's partner, Ms McClintock said.
When she got home and proceeded to take items out of the car, Edmonds "saw red", Ms McClintock said.
"He was dissatisfied with her answers to his questions," she said.
"He ran behind her and he pushed her over. There's no dispute that that happened."
Edmonds pleaded guilty to a charge of male assaults female over that incident yesterday.
"It's at this point that the Crown says Mr Bettink takes a step forward to intervene, but by now the defendant has lost it, he can no longer control his anger," Ms McClintock said.
Edmonds then allegedly attacked Mr Bettink, "unleashing a torrent of powerful blows to his face and his head".
The woman ran to the house to call police, and when she came back outside Edmonds had left and Mr Bettink was lying in a pool of blood.
When paramedics arrived, "it was too late", she said.
It was the Crown's argument that Edmonds' attack on Mr Bettink was "borne out of fury" at the woman and her relationship with another man, Ms McClintock said.
"This after he had constantly been calling her, texting her, and sending her money. The Crown says he must have been absolutely livid," she told the jury.
"When he attacked Bettink he did not do so to defend himself .... he went beserk.
"He viciously assaulted another man's head ... The force of that was such that he had to have appreciated that he could well kill Mr Bettink - and he did."
However, defence lawyer Simon Lance, in his brief opening statement to the jury, said that was not the case at all.
The two men had met "civilly" at the woman's house, he said, "they shook hands, had a cup of coffee" and talked through their issues.
"There's no suggestion that Mr Edmonds was 'livid' or enraged," Mr Lance said.
"And you will hear when he speaks to police he's very sorry for what happened and apologises to Mr Bettink's family. He did not want, or take any pleasure in, when he later found that Mr Bettink had died."
Mr Edmonds had defended himself against an attack by Mr Bettink, his lawyer said, "in the heat of the moment ... using his fists - no weapons".
"He's not thinking to himself, 'I'm going to kill Mr Bettink, I will carry on anyway'.
"The attack lasted 40 to 50 seconds. There was no conscious appreciation by Mr Edmonds that what he was doing was likely to cause death, and [he] just carried on anyway.
"This was a spur of the moment reaction to Mr Bettink actually punching him and he overdid it, and he's sorry for that."
The trial, before Justice Geoffrey Venning, is expected to last two weeks.
