A man who carried out a citizen's arrest on a home intruder was wrongly prosecuted for his murder, and will be allowed to pursue an estimated $1 million in legal costs from the State Government, the Sydney Supreme Court has found.

Key points: Last month, a trial jury found Benjamin Batterham not guilty of the 2016 murder and manslaughter of home intruder Richard Slater

Last month, a trial jury found Benjamin Batterham not guilty of the 2016 murder and manslaughter of home intruder Richard Slater Today, Supreme Court Judge Desmond Fagan found the decision to pursue charges was "unreasonable"

Today, Supreme Court Judge Desmond Fagan found the decision to pursue charges was "unreasonable" Mr Batterham may now apply to the NSW Attorney-General's Department for payment of all legal costs

Last month, a trial jury found Benjamin Batterham not guilty of the murder and manslaughter of Richard Slater, who broke into the 36-year-old's Newcastle home in 2016.

Following a struggle on the street outside, Mr Slater — who had methamphetamine in his system — suffered three heart attacks and died days later in hospital.

Mr Batterham, who was charged and prosecuted over the death, always claimed that despite allegedly saying he wanted "to kill" Mr Slater, he had put him in a choke hold to merely prevent his escape, and never intended for him to die.

But during his trial, the Crown argued he had been so angry at the burglar, who had entered his daughter's bedroom and stolen a handbag, that he had purposely applied the head lock to suffocate him, an argument the jury ultimately rejected in its verdict.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 15 seconds 1 m 15 s After the November trial, Mr Batterham spoke of his desire to move on with his life

'Acted lawfully and reasonably'

Today, Supreme Court Judge Desmond Fagan found the decision by prosecutors to pursue charges against Mr Batterham over the death were "unreasonable" on the basis that medical reports had strongly supported the conclusion Mr Slater's cardiac arrests after the struggle and subsequent death were caused by his methamphetamine use and a heart condition had developed as a result of that drug abuse.

"Mr Batterham acted lawfully and reasonably in chasing Ricky Slater when he found him intruding in his home and stealing property," Justice Fagan said.

Mr Batterham always maintained he used a head lock to simply restrain Mr Slater, not to kill him. ( Supplied )

"He acted lawfully in first calling the police and then restraining Slater until officers arrived.

"In my view, the decision to charge Mr Batterham would have been unreasonable even if the prosecution had been in possession of only the evidence that had emerged by the end of the committal [hearing]."

The judge referred to a key report by toxicologist and pharmacologist Michael Kennedy, which was produced in March this year, about eight months before the trial.

He noted Dr Kennedy's report found Mr Slater's cardiac arrest had, "resulted from causes independent of the alleged acts of the accused, namely from cardiomyopathy, methamphetamine in the deceased's blood and maximal exertion on his part [during the struggle]".

'Charge should have been withdrawn'

Justice Fagan noted that conclusion was supported by a number of other doctors, and that those opinions collectively, "gave rise to a reasonable doubt as to whether the alleged acts of the accused [Mr Batterham] had been a substantial cause of death".

"There is no basis upon which the jury could reasonably have rejected the opinions of Drs Kennedy, Vuletic, Duflou and Professor Christie or failed to find that those opinions gave rise to at least a reasonable doubt," he said.

"If the prosecution had also been in possession of Dr Kennedy's medical opinions when the charge was laid in late March 2016, the unreasonableness of prosecuting for murder would have been clearer still.

"The charge should have been withdrawn upon receipts of Dr Kennedy's report."

Mr Batterham caught the burglar breaking into his home (pictured) during the Easter long weekend in 2016. ( ABC News: Giselle Wakatama )

Justice Fagan noted there had been significant public discussion about what rights residents had to apprehend a home intruder, or other people committing an offence, in circumstances where that citizen's arrest caused death.

But he noted this issue was not really tested by the case because, "it was not proved that Mr Batterham's acts were a contributing cause of Ricky Slater's death".

"The law is clear that only reasonable force may be used in an arrest," Justice Fagan said.

He granted Mr Batterham a certificate of costs, which would allow him to apply to the Attorney-General's Department for payment of all legal costs he incurred for his defence.

Lawyers for Mr Batterham said they were preparing an itemised account of those costs, which they said were likely to exceed $1 million.