After a night of threats and abuse by text message, it was six frenetic minutes from Timothy John Constable's arrival at a Christchurch house to when he lay dead in the gutter.

The 24-year-old P-user died outside the house in the suburb of Burnside with his skull smashed and a stab wound near the heart.

Some of those present tried CPR but the stab wound had severed his aorta, the blood vessel leading from the heart, and there was no chance of saving him.

The crown says 21-year-old Adam Robert Gempton stabbed Mr Constable.

Crown prosecutor Deirdre Elsmore told the jury at the start of the four-week murder trial in the High Court at Christchurch that Gempton had an issue to settle with Mr Constable, believing he was a police informer who had "narked" on a friend.

Three men are on trial for Mr Constable's murder on August 7, 2009, and two of the women present on the night have been charged with assaulting him. The crown has decided not to proceed with an assault charge that had been laid earlier against Correna Anne Coombs, 41.

Gempton, Steven Wayne Bright, 26, and Levi Michael Coombs, 18, are charged with murder, while Shaharna Margaret Hickey, 23, and Shahana Mikena Coombs, 21, are charged with assault. They deny all charges.

The crown will call evidence from 57 witnesses in the trial before Justice Lester Chisholm and a jury.

Mrs Elsmore said the crown would allege that Mr Constable died almost instantly from one of four stab wounds inflicted by Gempton. Levi Coombs had struck him in the body and head - breaking his skull - with a wooden patu, a Maori club. Bright had punched and kicked him, and both women had punched him during the attack.

She said Mr Constable had problems of his own and was an occasional methamphetamine user. He was in a volatile relationship with Gisinda Nancy Marie Coombs, the sister of Levi and Shahana Coombs.

The couple had argued and not spoken for a couple of days when Gisinda began texting and asked Mr Constable to the property in Todd Avenue, Burnside, where family and friends were socialising and drinking.

Texts were exchanged during the evening between Mr Constable and several of those present. They become more threatening and aggressive as the evening went on, and Mr Constable used the word "nigger" in a text which appeared to upset people.

Mrs Elsmore also said Gempton believed Mr Constable had "narked" to the police about a friend. Gempton texted a friend that night: "He's going down. I'm going to stab him."

She described what she said were six "frenetic" minutes when Mr Constable arrived outside the house to pick up his girlfriend, Gisinda Coombs.

Someone saw he was holding a pistol, which two of those present knew was an imitation gun, she said. Someone called out, "He's got a gun," and the attack began. Gempton used a knife he had taken from the kitchen and put in his pocket, and stabbed him four times, Mrs Elsmore said.

Gisinda Coombs put her body over his as he lay dying in the gutter from his stab wounds, and with a fractured skull from a blow by Levi Coombs. Bright then kicked him in the head, and though he and a neighbour tried to resuscitate Mr Constable, he died almost immediately.