Mr Day died at the age of 35 in July 2018 when his throat was cut, but his issues with the two men convicted over their involvement in the crime started at least a year earlier - much of it playing out in Wangaratta's Ryan Avenue in Victoria's north-east.

The sentencing of Darcy McNamara and Phillip Dunn in the Supreme Court marked the end of a tragic time, but did not provide much clarity of what really happened.

"Their relationships were complex and changeable," Justice Michael Croucher said of the three men.

"Like Mr Day, Mr McNamara and Mr Dunn were heavy drinkers.

"There were episodes of aggression, fighting, property damage or threats between each of them."

McNamara, 44, was actually in a better living situation at the time of committing murder than he had been in his adult life.

He described the government-supported housing where he had lived in Wangaratta for two years as "the first time I had a nice safe place and stability in my life".

Before then, he had experienced periods of homelessness in Melbourne and Sydney.

With a "low average" IQ of 87, McNamara had also reported various head injuries with loss of consciousness from being hit by a car and playing rugby league.

He said his childhood "wasn't one of loving and nurturing" and was marked with tragedy - not only was he abused, his father put his mother in a coma and shot himself when McNamara was just 10 or 11 years old.

Justice Croucher took this into account when handing down a sentence, but did not allow it to be an excuse for committing murder decades later.

McNamara was sentenced to 20 years in jail, with a minimum of 14 before he will be eligible for parole.

In the first recorded police incident between the two men, McNamara was the victim.

Mr Day was charged with criminal damage for smashing windows at his home in December 2017, but by Christmas that year, they had patched up their differences.

Justice Croucher described them as "drinking chums", but this was not always positive.

"Since the age of 17, Mr McNamara has had a history of intermittent heavy alcohol use," he said.

"He would drink up to four litres of cask wine or two bottles of spirits from 9am each day. He conceded that his life 'has been fully ruined by alcohol (which) caused so much pain, grief, and heartache' and that alcohol 'doesn't agree with (him)'."

Despite this, McNamara, Dunn and Mr Day had all been drinking at the time of the murder. That had not been the first violent altercation between them.

At different times in early 2018, McNamara was seen threatening to kill Mr Day, punching him in the face and swinging a sock full of rocks at him.

On that last occasion, the two men were seen to again patch up their differences and walk home together.

But on what Justice Croucher described as "a cool-ish winter evening in Wangaratta", the violence went well beyond threats or punching.

It would be six weeks after Mr Day's death that his body was found buried in a shallow grave in the garden of McNamara's home.

The decision of McNamara and Dunn to blame each other for cutting Mr Day's throat means the true story of how it happened will remain a mystery.

On McNamara's version of events, he woke up to find his pants were down and Dunn and Mr Day were fighting in his home.

He told police Dunn said "poofter was trying to rape you".

This was not the first time a sexual relationship between McNamara and Mr Day had been referred to in court, but on this occasion, McNamara admitted he "lost it" and became angry.

He insisted he encouraged Dunn to kill Mr Day there, and pleaded guilty to murder on that basis.

But Dunn was convicted of assisting an offender, claiming he was outside behind the screen door when the murder happened.

He told a friend "Darcy's f---ing mad and took it too far".

The offences each of the men pleaded guilty to was the difference between their sentences - McNamara will not be released for more than a decade, while Dunn will be out on Wednesday.

Mr Day had lived at Dunn's home for a short time in 2017, but that arrangement ended in a fight, and the animosity continued.

The day of the murder, July 26, 2018, started as another day with petty disputes when Dunn called triple zero at 2.08pm to report McNamara and "some bloke that I knew a fair while ago" were trespassing, breaking windows and attempting to gain entry to his house.

While the prosecution could not prove it, they said it was likely the "other bloke" was Mr Day.

Dunn, now 61, has a long history of mental illness, having been diagnosed with bipolar when he was 36, and has been admitted as a psychiatric inpatient five or six times, including at Kerferd Psychiatric Unit at Wangaratta hospital.

Justice Croucher acknowledged it was "quite odd" that McNamara and Dunn could plead guilty using completely different versions of what they said happened to Mr Day, but it was acceptable under the law.

"The law at once requires each accused's case to be considered separately, and allows the Director (of Public Prosecutions) the discretion to prosecute each accused separately, based on what may be proved on the evidence admissible in the case at hand," he said.

He also acknowledged this would require "mental gymnastics" from Mr Day's family in processing their grief and the court proceedings.

Mr Day, who was known to many of his friends as "Pockets", himself had longstanding issues with alcohol abuse. He was also homeless and often camped under bridges along the Ovens River or slept on the couches of various friends.

One of those people was Betty Torney, who he called "Gran" and who supported him with food and money after they met through Victory Church - located on Ryan Avenue, not far from McNamara's house.

Mr Day is survived by his mother Marilyn Chambers, sister Cherrona Day and his former partner Jade Griffiths, who is the mother of his eight-year-old son.

It was these three women who made emotional pleas for information on his whereabouts when he was reported missing in 2018, and who made victim impact statements to explain to Justice Croucher the impact of his murder.

"Ms Chambers struggles with the tension that her son's difficulties with drugs and alcohol created between them, and feels she might have done more to help," Justice Croucher said.

"Since his death, she finds herself crying a lot, being sad or angry all the time, and lacking in motivation.

"It pains her that she never got to say goodbye."

Mr Day was Ms Griffiths' first love.

"She remembers his bubbly personality and cheeky smile, which their son has inherited," Justice Croucher said. "While his difficulties made it impossible to stay with him and raise a child together, she still loved him and despairs that their son has lost his father.

"Ms Griffiths suffers nightmares about Mr Day's last moments, has become depressed and feels as though a piece of her has died."

In speaking to a psychologist earlier this year, McNamara revealed he was anxious about the court proceedings and was also having nightmares while contemplating "the full circumstances of Nathan's death".

He told police at the time of his arrest he was "not remorseless" and was asked by officers how he felt knowing Mr Day's body had been recovered.

"I suppose it's about getting some closure and his family and that," he said. "And that I was a friend.

"And - as hurtful as it may be - by going through these steps, as hard as it is, at least the answers will be known.

"And I feel very sad about the whole thing."