Was Neville Butler's death caused by his niece and her partner's alleged assault on him or something else such as over-consumption of alcohol?

A jury in the High Court at Rotorua is being asked to decide when its members deliberate at the end of the manslaughter case the Crown has brought against Carlos Uerata, 26, and Zyla Adonia Loudene Monilita Brittany Tigerlily Butler, 21.

Both denied the charge laid separately against them when their trial opened today.

Outlining the events of the early hours of September 26, 2017, at a flat in Rotorua's Steeles Lane, prosecutor Anna McConachy said that in the hours preceding Butler's death he and others had been celebrating his niece's 21st birthday.

Two people are on trial for manslaughter in the High Court at Rotorua. Photo / File
Two people are on trial for manslaughter in the High Court at Rotorua. Photo / File

The issue, McConachy said, was what happened between the last guest leaving at 2.15am and Zyla Butler calling an ambulance around three hours later.

By then Neville Butler was unconscious and couldn't be resuscitated.

McConachy claimed Zyla Butler told the 111 operator her uncle had passed out, wouldn't wake up, saying "we choked him out".

In a call made six minutes later, Uerata said Butler had passed away, or if not he was unconscious. Asked what happened, the line went dead.

McConachy alleged Zyla Butler told the police her uncle, who'd been drinking heavily, had been kicking things around, fought with Uerata then pulled her on to a couch.

Uerata attempted to pull him off and tried to "choke him out". Neville Butler was snoring on the floor and didn't wake up, his niece allegedly told police.

"She said she was freaking out and Carlos told her her uncle would be all right and get up soon but he never got up," the prosecutor said.

Uerata told police Butler had crashed out on the floor but he denied putting his niece's uncle in a choke hold.

Two people are on trial for manslaughter in the High Court at Rotorua. Photo / File
Two people are on trial for manslaughter in the High Court at Rotorua. Photo / File

McConachy said the jury may conclude Butler's death was a tragic accident but it was the Crown's case the defendants had caused that death by unlawful acts, assaulting him in a way that amounted to manslaughter.

She defined the assaults as Uerata putting a choke hold on Butler and Zyla Butler holding her uncle's arms, together effectively rendering him unconscious and unable to defend himself.

A post-mortem examination revealed Neville Butler had extensive neck and carotid artery bruising. A pathologist concluded his death had been caused by asphyxiation.

Uerata's lawyer, Bill Lawson, said one of the major issues the jury would have to decide was whether the defendants' actions caused Butler's death, or whether something such as health issues or the amount of alcohol he'd drunk led to it.

"Uerata was whānau, he loved [Butler]" Lawson said, reminding jurors Butler had become so unruly after drinking a lot at the party he'd had to be restrained.

The lawyer submitted self-defence wasn't an unlawful act.

For Zyla Butler, Philip Morgan, QC, indicated the issue for the jury was what, if any, part she played in the events of the night her uncle died.

"Zyla told police she was overcome with grief, overcome by alcohol and had not slept for three days, so to what extent can you rely on anything she said when she was in that state?" he queried.

Neville Butler's partner, Dana Corbett, testified she'd fallen in love with him in 2016. He'd then spent time in prison but they'd rekindled their relationship on his release just days before his death.

"He was really positive and excited to be home, he was working out, lovable, really affectionate, he did no more drugs but did drink alcohol, he was never aggressive or violent."

Corbett wasn't aware of any medical problems he may have had.

The trial, which is before Justice Graham Lang, is scheduled to conclude on Friday.