Three teenagers accused of assaulting a homeless man before he died will give evidence at the trial of a 14-year-old boy accused of killing him.

The Crown alleges the accused stabbed 40-year-old Kelly Donner four times over a dispute about a torch he borrowed from the victim.

Kelly was found severely injured on a grassy area near the Flax Bar and Eatery at about 10:30pm on Sunday, 4 March.

Yesterday, The High Court in Napier was shown CCTV footage of teenager riding around on a bike with a bloodied knife, shortly after Kelly was stabbed.

Footage of the accused and four other teenagers throwing bottles, rocks and a bicycle at Kelly was also shown.

Two youths who have appeared in Hastings Youth Court in relation to Kelly's death and another teenage witness are due to give evidence this morning.

The Crown said they would give an eye witness account of the attack, including evidence that the alleged offender told one of them that he had stabbed Kelly.

On Tuesday, the court heard evidence from Detective James Forgie, who analysed the CCTV footage taken from behind the Flax Bar and Eatery and also from a camera attached to the outside of the Flaxmere Library overlooking the back of the pub.

It showed five youths attacking Kelly with rocks and one throwing a bicycle at him.

He says the video then showed the accused coming out of a shadowed area at the back of the pub with a knife in his hand and following Kelly off-screen.

Thirty-three seconds later it showed him coming back into view of the CCTV camera with what Detective Forgie said was a "bloodied knife" in his hand.

The accused then picked up his bike that was thrown at Kelly and rides around.

"He's on the bike with the knife in his left hand," Detective Forgie told the court.

The accused's shoes also appeared to be bloodied, the court heard.

Earlier in the day, Institute of Environment Science and Research forensic scientist Janina Hopkins said an analysis of a black leather vest worn by the teenager that night, later found at a Flaxmere address, had found blood stains on it.

"There were numerous blood stains present on the inside and outside of the vest."

Giving evidence, forensic pathologist Thambirajah Balanchandra said Kelly suffered 14 cuts.

The carotid artery in his neck was completely severed and he bled to death, he said.

Without medical intervention Kelly would have only had between two to five minutes to live, he said.

The carotid artery was a major artery carrying blood from the heart to the brain and once it was severed Kelly's organs and brain would have suffered from the lack of blood and oxygen, Dr Balanchandra said.

Kelly also suffered a fractured rib, minor fractures to his eye socket and bruising or bleeding to his frontal lobe, as well as several lacerations to his scalp, he said.

Kelly's family wept as his wounds were described in court.

Under cross examination by the defendant's lawyer, Dr Balanchandra said Kelly also had THC in his blood.

THC is the active ingredient most commonly associated with cannabis.

"Eighteen micrograms per litre of blood is consistent of smoking a single cannabis cigarette within two hours of death," Dr Balanchandra said.

Kelly also had two "superficial stab wounds" to his chest and shoulder, he said.