The jury at Justin Christopher Bennett's manslaughter trial in Saint John heard testimony Tuesday about an altercation over a computer modem that led to the 19-year-old's uncle, Scott Bennett, being fatally stabbed last winter.

"I could hear Scott asking for help and I could see blood pooling under the door," testified Dean Haley, who was at the centre of Feb. 4, 2015 incident on the city's east side.

Saint John homicide investigation

Scott Bennett, 32, was stabbed in a "violent altercation" at a house on Norris Road on Feb. 4, 2015, and later died in hospital. (Matthew Bingley/CBC)

Haley, 20, told the Court of Queen's Bench that he and a 15-year-old boy, who cannot be named because of a publication ban, were visiting the accused that night at his grandmother Wendy Bennett's home, where he had lived for the previous two years.

Scott Bennett, 32, who did not live at the house, arrived looking to take his mother's computer modem, said Haley. Justin Bennett initially resisted and Scott Bennett turned angry, he said.

"He said we were all pukes and he was going to smash us."

Justin Bennett handed over the modem, but as Scott Bennett was leaving, Haley decided to challenge him, asking him to repeat the insult. It's a decision he regrets to this day, he told the courtroom.

"He (Scott) called me a puke and then spit in my face," testified Haley. The situation deteriorated from there, he said.

Scott Bennett, who Haley said outweighed him by about 65 pounds, punched him in the face under his right eye, he testified. Haley said he threw a punch in return, but then blacked out — a symptom, he said, of his autism.

'It was self-defence'

The other visitor that evening told court the fight was not going well for Haley, who was mostly trying to cover his head and "flailing" his arms when trying to strike back.

The boy said he then heard Justin Bennett yell, "Stop!"

When the fight continued, he saw Justin Bennett raise a knife, he said.

"Justin stabs Scott," the boy testified.

"What did you do then?" asked Crown prosecutor Kelly Winchester.

"I looked down. I didn't want to see the sight of blood," he said.

The jury also heard a recording of the 14-minute long 911 call the boy made following the stabbing.

In the background, Justin Bennett can be heard on the phone with his grandmother — Scott Bennett's mother — trying to explain what happened.

"It was self-defence," a voice cries out.

Earlier on Tuesday, Wendy Bennett also testified about that phone call from her grandson.

"Nanny, nanny, nanny, I love you. I'm sorry, I'm so sorry," she said Justin Bennett told her.

Scott Bennett, who was severely injured, was transported by ambulance to the Saint John Regional Hospital, where he later died.

Wendy Bennett said her son had a serious crack cocaine addiction, which he had struggled with since he was 16 years old.

She told the court the addiction had worsened in the year before his death and it was not unusual for him to ask her for money, or to steal household items to raise money to feed the addiction.

Just days before the night in question, he had taken her modem back to his trailer and Justin Bennett had retrieved it, she said.

The knife used in the incident had been given to Justin Bennett as a present from his late grandfather, who had received it as a retirement gift, said Wendy Bennett.

"He liked knives," she said of her grandson.

The trial, which started on Monday, resumes on Wednesday.