Reay was on Wednesday found guilty of murder over the strangulation death of Geoffrey Fardell in the Mid North Coast Correctional Centre in June 2019.

The 46-year-old earlier this month pleaded not guilty to murder but guilty to manslaughter on the basis of excessive self-defence and had faced a two-week judge-alone trial in Port Macquarie Supreme Court.

Reay, who for the past two decades and across two states has established an almost unparalleled reputation for random and unprovoked acts of extreme violence, mayhem and bizarre behaviour behind bars, strangled Mr Fardell in a cell at the jail, near Kempsey, between when the pair were locked into cell 234 in F-pod at 3.20pm on June 10 and when another inmate did the morning milk rounds at 6.09am on June 11.

Mr Fardell was found face down under a blanket on the floor of the cell with ligature marks around his neck.

Police were unable to find what was used to strangle him. Reay gave evidence during the trial, claiming Mr Fardell attacked him on his bunk and repeatedly punched him in the face after an argument over the volume of the television in the cell.

Reay said while he was being punched he managed to reach up and in "one motion" grabbed a makeshift clothesline from above his head and wrapped it around Mr Fardell's neck.

"I was hoping that the punches would come to a stop, but they didn't," Reay claimed. "The more the flurry of punches came the tighter I went."

He said eventually Mr Fardell "flopped" on top of him and then onto the floor of the cell and he removed the clothesline from his neck.

"I was in fear for my safety," Reay said. "You don't know who you're in a cell with and what they're in for."

But during his closing address, Crown prosecutor John Stanhope set out for Justice Robert Hulme the reasons why he would reject Reay's version of what happened inside the cell and his claim that he was acting in self-defence.

Mr Stanhope said it was "inherently implausible" that Mr Fardell would attack Reay over the volume of the television in the cell, as Reay had claimed, and said there was not sufficient room in the 4 metre x 2 metre cell for the attack to have occurred in the way Reay described.

He said Reay had given evidence that he had suffered a split lip from Mr Fardell's purported attack, but he had not mentioned any injuries to police at the time of Mr Fardell's death.

"Perhaps more significant than the inconsistency about the injury to the face and the lack of complaint is the proposition that in his evidence he described being punched with a flurry of punches several times," Mr Stanhope said. "If that were true, then addition to there being the possibility of injury to the lip area, we would see some bruising to other areas of the face of the accused. None of that is visible in the photographs, none of that is observed by any other witness."

Mr Stanhope highlighted that while Reay said he had felt "vulnerable" on his bunk, he did not say he was acting out of fear when he grabbed the makeshift clothesline and strangled Mr Fardell.

"He said he was acting on an impulse," Mr Stanhope said.

He said the evidence in the trial showed not only that Reay had a tendency to be violent but that he was not a credible or reliable witness and said if Justice Hulme was not convinced of Reay's version then he should be convicted of murder.

After picking apart Reay's version of what he said happened in the cell, Justice Hulme concluded that he did not believe any of it.

He found that Mr Fardell had not attacked Reay and had not committed suicide and was satisfied that Reay had strangled him to death.

"The accused's account of being attacked by the deceased and thinking it was necessary to defend himself from this attack is entirely implausible," Justice Hulme said. "To put it in simple terms, I do not believe any of it." Justice Hulme also found that Reay had not attempted to administer CPR or call for help after strangling Mr Fardell.

"If Mr Fardell was not already dead then the accused was content to see him die," Justice Hulme said.

Reay's matter will next be mentioned on April 16 to get a sentence date.

Mr Fardell's mother, Sandra Deveson, spoke to the Newcastle Herald at the outset of the trial about her shock and grief at learning her son had been killed behind bars, compounded by her discovery of Reay's extensive history of extreme violence.

"I was just absolutely horrified," Ms Deveson said. "I just could not believe it. You have a sense that he is in protective custody and he is going to be OK. I asked the question: 'What is the screening process where you put people together?' The response was: 'we're reviewing it'. Later, I asked the question again: 'Who does the screening process?'"

Ms Deveson says she was told there was an administrative process that determined which offenders were placed together.

"So what information have they got to see that [Reay] is high risk and shouldn't be in a cell with anybody else," Ms Deveson said.

Reay's notorious reputation behind prison walls includes dozens of assaults on prison officers, fellow inmates and jail staff as well as bizarre and compulsive behaviour like "simulating grave digging", drinking and showering from his toilet and "persistent masturbating", according to court documents and prison records.

In Queensland, Reay's reputation caused specific changes to cells that housed him, his interaction with other people became almost non-existent and when he had to be moved over the border it became a police operation performed with teams of officers and military precision.

Assessments warned of him killing or maiming people who came into contact with him.

And in NSW, Reay's conduct in jail meant authorities considered him such a threat that in 2014 the state applied to have him declared a "high risk violent offender" and he was detained for an additional 12 months at the conclusion of his jail term.

And as far back as October 2003, Queensland prison records highlighted that "there is a high risk of [Reay] killing or seriously injuring other prisoners or persons whom he may come into contact with."

And it appears the years behind bars haven't made him any less volatile or violent.

About 10 years after that assessment in QLD, a psychologist in the prison system in NSW conducted a risk assessment of Reay and formed the opinion that his "risk of future violence would likely include the real potential for further 'serious' violence" and Reay "seemed unable to comprehend the severity of his violent conduct over the years".

Those ominous premonitions came true time and time again in prisons in Queensland and NSW and have led to Reay spending almost all of the last 17 years behind bars as he has repeatedly bashed staff and inmates.

Reay was serving a sentence for affray in March 2019 when he assaulted a prison officer at Lithgow Correctional Centre.

In June that year he was sentenced to a further 12 months in jail and a few days later murdered Mr Fardell at Mid North Coast Correctional Centre.

Meanwhile, Mr Fardell, from Ballina, was expected to face Ballina Local Court a week after his death on charges of driving while under the influence of prohibited drugs, destroying or damaging property, intimidation and breaching an apprehended domestic violence order.

He had been in custody less than three months and had been moved from Grafton Correctional Centre to Mid North Coast Correctional Centre after it is believed he had been receiving threats.

He arrived at the jail outside Kempsey on the same day as Reay and a few days later - despite his mother being assured he would be placed into protective custody - Mr Fardell was moved into a cell with one of the state's most violent inmates.

About a week later, Mr Fardell was found dead, strangled in the night while the cell door was closed.

Stocky, with a shaved head and a thick, plaited mullet, Reay had asked to appear via audio visual link from jail during the trial rather than in person as is customary.

Dressed in prison greens he remained handcuffed throughout the proceedings, interjecting occasionally and repeatedly stood up to stretch. He appeared to be reading from a bible while Justice Hulme delivered his lengthy judgment on Wednesday. The murder charge against him does not seem to have deterred Reay from reacting violently or led to him being completely segregated from other inmates.

Court documents reveal Reay was convicted last month of assaulting another inmate at Cessnock Correctional Centre late last year and had another 12 months added to his sentence.

"The general public out there should be extremely concerned if he is ever released," Ms Deveson said of Reay. As for her son, Ms Deveson said she missed catching up for coffee or a swim in Ballina. "He was generous to a fault," Ms Deveson said of her son. "He was always happy. He didn't hold any anger and he had heaps to be angry about. He was great to be around."