But the jury that acquitted Daniel James Sharpe of murder was not told about this, or other evidence that prosecutors wanted to rely on, after a judge excluded it from the young man's trial.

Sharpe, now 20, was early this year found guilty of the lesser offence of manslaughter over the April 2019 stabbing death of 29-year-old Andrew Drake in Surfside.

Justice Geoffrey Bellew later said the jury must have believed Sharpe was acting in defence of himself and his father, albeit with excessive force, when a fight broke out between Mr Drake and Sharpe's dad.

The NSW Supreme Court judge sentenced Sharpe last week to seven years and six months in jail, with a non-parole period that will expire in October 2024.

It can now be revealed that Justice Bellew declined applications by the Crown to put certain evidence before the jury.

In one pre-trial determination, he ordered the exclusion of what he deemed to be irrelevant evidence about Sharpe's behaviour on the evening of Mr Drake's death.

A man named Glenn Martin, who lived in the area in question, had given police a statement about having gone to the Sharpe property with his girlfriend not long before the stabbing.

He said he had seen Sharpe, then 18, holding what looked like "a short version of a shotgun".

"[Sharpe] lifted it up with both hands," Mr Martin told police.

"He pointed it towards us and directed more towards me."

He went on to say that while his girlfriend had been speaking to Sharpe's father, Sharpe had walked into a shed and emerged with what appeared to be a hunting knife in his hand.

"[Sharpe] was moving it back and forth and I could tell he was agitated," Mr Martin said.

"He just looked like he was wired up and ready to go. I just got the feeling he wanted to use it.

"If I went in that yard, he would have went me [sic] without a doubt."

Prosecutors said this was relevant and admissible evidence about Sharpe's state of mind at or about the time of the stabbing.

But Sharpe's barrister, Troy Anderson, argued it was not relevant and that there was a substantial risk the jury would "misuse" the evidence if it were admitted.

Justice Bellew, in deciding ahead of the trial to exclude the evidence, found that the apparent holding of the gun and knife were "isolated acts", "unaccompanied by any act of aggression".

In another instance, Crown prosecutor Kate Ratcliffe had hoped to tender during the trial extracts of two conversations between Sharpe and his father.

The expletive-laden exchanges, which were captured by a listening device before Sharpe was remanded in custody, included the then-teenager telling his dad: "You didn't have the c--- on the ground going, 'Die c---, die c---, die c---'."

Mr Anderson submitted, however, that the contents of the conversations were "misleading and confusing", with Sharpe having described the incident in ways that were inconsistent with the case against him.

Justice Bellew agreed, finding that while the evidence of the conversations was relevant, its probative value would be substantially outweighed by the danger of unfair prejudice.

"I concluded that there was a considerable risk that if the evidence were admitted it would have done nothing other than portray [Sharpe] in an unfavourable light, in circumstances where what he described in terms of his altercation with the deceased formed no part of the Crown case against him, and was inconsistent with expert evidence upon which the Crown relied," he said.

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