Adrian Phillips has been found guilty of murdering father-of-one Bayden Williams.

The jury reached its unanimous verdict in the High Court at Hamilton today after a five-week trial.

Phillips, 24, shot Williams three times on the night of August 5, 2020 after ramming his car off the Kopu-Hikuai Rd near Thames.

The Ngatea man claimed he shot Williams, 20, in self-defence as Williams lunged at him but the Crown said Phillips was an angry, aggressive man who harboured a grudge against his former friend after Williams got the upper hand against him in a fight eight months earlier.

The Crown said Phillips shunted Williams off the road after intercepting the Tairua man who was driving over the windy, isolated road to meet his ex-girlfriend Chloe Randall and their baby son for dinner.

Phillips was in a relationship with Chloe's twin sister Macy Randall and was unhappy about the prospect of Chloe and Williams rekindling their relationship.

Phillips told the jury earlier in the trial he wanted an apology from Williams who put him in a headlock and held him down while Macy and Chloe's father Peter Randall fought with Williams' father Lance Williams on January 11 that year.

Crown prosecutor Jacinda Hamilton said Phillips felt "embarrassed, humiliated and emasculated" afterward and made a number of threats of violence and seeking revenge against Williams to friends, including the day before he shot him.

Hamilton said by early that year Phillips had a short fuse, was triggered to anger easily and was having daily rages, including at Macy.

She said Phillips was seeing a psychologist for his mental health and had insight into his anger and knew how to avoid situations that triggered his temper, but ignored them.

Phillips illegally bought the sawn-off shotgun and ammunition in the weeks before the shooting.

Bayden Williams' body was discovered on the Kopu-Hikuai Rd near Thames on the night of August 5, 2020. He had been shot three times. Photo / NZME

The Crown said Phillips confronted Williams with the intention of frightening, intimidating and potentially hurting him, and needed a weapon to have the confidence to do it.

Hamilton said Phillips must have known that when he shot Williams in the head it would kill him and therefore it was intended. That shot on the roadside was immediately fatal.

Phillips had already shot Williams in the thigh and shoulder.

The Crown said Williams was crouching by his car down the bank with a shotgun wound to his leg when Phillips shot him in the left shoulder.

Hamilton said Phillips was the aggressor, not the other way around, and that Phillips' version of the event changed and this damaged his credibility.

This included whether he had the gun when he got out of his ute or went to retrieve it because Hamilton said if he went to retrieve it he could have driven away.

But defence counsel Ron Mansfield, QC, said Williams was charging up the bank threatening: "I will cut you up, I will f**ken kill you," when Phillips initially froze then panicked and loaded and fired the gun.

He said Williams kept charging up the bank despite being shot twice, and that Phillips believed Williams was carrying a knife and would stab him.

Mansfield said Williams was known to carry a knife, had been violent toward Chloe in the past, and lunged toward Phillips.

He said Phillips acted in self-defence and out of fear for his life when he fired the fatal shot to the head.

He said Phillips was acutely mentally unwell at the time of the incident following a downward spiral after a traumatic accident in which Phillips set himself alight while pouring accelerant on a bonfire two years earlier.

Mansfield said Phillips had been consistent in his accounts of the incident, including that he thought Williams had a knife, and that Williams did have a knife in his bum bag that night.

He said expert psychiatric opinion was that Phillips had a panic attack at the moment he thought Williams would kill him and was likely to be "disassociated" at the time.

Phillips was not an angry man, but rather a "very sick man" who had not been violent before.

In summing up today, Justice Melanie Harland told the jury they had to answer a number of questions in deciding whether the Crown had proven Phillips was guilty of murder.

"You need to consider whether the defensive action was reasonably proportionate to the perceived danger."

If the jury cannot find Phillips guilty of murder, then it is open to them to find him guilty of manslaughter.

"Your verdict is important ... you must take the time you need. Justice is not delivered under pressure."