A man on trial for murdering his girlfriend admits he pointed a gun at her, pulled the trigger, and shot her in the head.

But, Tuaine Llewellyn Bevan, 28, told the High Court at Palmerston North yesterday, he didn't think the gun was loaded when he was "mucking around" with it.

The shot killed 23-year-old Stacey Lake in the bedroom of the Ngaio St, Otaki Beach, house she shared with Bevan. It was fired about 4pm on May 8 last year.

The Crown says he shot her at close range because of a domestic dispute, while the defence says the shooting was an accident.

In front of Justice Jillian Mallon and a jury, Bevan described how Ms Lake was lying on the bed when he knelt and pointed the gun at her.

"I thought it was safe. I had the magazine in my hand.

"I thought there was no bullet at all in the chamber and let off a shot," Bevan said.

"I must have clicked the trigger and the gun goes off. As it goes off I got a fright and thought f..., ‘what just went on?' F... I was shocked."

Bevan denied that he intended to kill Ms Lake, even momentarily.

Crown prosecutor Paul Murray asked why Bevan pointed the gun at Ms Lake.

"Just mucking round. I'm not doing it to intimidate her."

"What was going through your head?" Mr Murray asked.

"Just that nothing can happen. There's no way that I can harm her," Bevan said.

Ms Lake's eyes were closed.

"She doesn't have any idea that the gun's pointing at her. She's just lying there."

Bevan said he retrieved the gun from his family home earlier in the afternoon, but Mr Murray suggested he went and got it about half an hour before the shooting.

Earlier in the day Bevan and Ms Lake continued their ongoing domestic dispute and Bevan said he punched a fridge door and threw some household items on the ground.

He admitted "losing the plot", but said he did not lay a hand on Ms Lake, nor had she touched him.

Scratches on his face were from breaking a drawer over his head.

"I just pulled it out and put my head through it."

Three days before the shooting the pair had been fighting. Bevan said Ms Lake ran at him and he shoved her away with his palm, leaving her with a black eye.

Bevan said the pair got together at a 2006 New Year's Eve party. They have a daughter.

When opening the defence case, lawyer Christopher Stevenson reminded the jury that Bevan did not have to give evidence and doing so was “difficult and stressful”.

Earlier in the day the last Crown witness, ESR scientist Angus Newton, said the gun was probably 5 to 20cm away from Ms Lake when it fired.

The lawyers will sum up today.