On October 25 in 2016, Blackler and Fahey had a day-long drinking session at their Brockville Rd flat, washing down almost a whole bottle of Jagermeister with a box of beers.
But the mood soured late in the evening.
According to Blackler, Fahey - known to his mates as "God" or "Grumpy Old Decorator" - made sexually inappropriate comments about his terminally-ill sister.
Justice Dunningham said that saw the defendant become enraged and deliver several blows, at least one of which was inflicted while the man was on the ground.
He also suggested Blackler may have "subdued" his flatmate using a singlet which was found bloodied near the body.
That was disputed by defence counsel Anne Stevens and Justice Dunningham said the medical evidence did not support the proposition the garment had been used as a ligature to strangle the victim.
Bloody footprints from Fahey's body leading to the bathroom showed Blackler tried to wash himself after the attack but he could not cleanse himself of all evidence of the attack, the Crown said.
A taxi he took from his house to his then partner's address in Corstorphine that night was combed by forensic investigators.
They found traces of blood 600,000 million times more likely to be from Fahey than anyone else in the country on a passenger seat panel.
"You knew when you left the house you had killed or probably killed him... and you did nothing about that," Justice Dunningham said.
Blackler's girlfriend gave evidence at the trial that nothing was said about the incident over the course of the eight hours they spent together.
But her teenage daughter told the jury a different story.
She overheard Blackler telling her mother he thought he had killed his best friend.
Pathologist Dr Martin Sage could not make a definitive finding on what killed Fahey, noting the man suffered severe heart problems as well as lung disease.
Though he described the cuts and bruises to the victim's face and the small broken bone in his throat as "non-fatal", he said there was nothing to indicate he would have died without the assault.
The video of Blackler's police interview saw him cry and sob repeated apologies to his dead flatmate.
"He was like my dad that I never had," he said.
Stevens said her client's grief was apparent in that interview.
Though she had to accept the jury found the attack by Blackler was an operative and substantial cause of death, she pointed to the evidence of Dr Sage.
He presented a complex picture of Fahey's health, Stevens said, including issues related to age, alcoholism, ill-health in the days leading up to death and very severe coronary disease.
The court heard this morning Blackler was subject to release conditions at the time he killed his friend and had a lengthy criminal history.
He had 150 convictions, 17 of which were for violence, including threats and weapons charges, Justice Dunningham said.
The Otago Daily Times revealed, after the guilty verdict was given by the jury, that Blackler had stabbed his dog with hedge clippers two and a half years before committing the manslaughter.
As was the case with Fahey, he described the victim as his "best friend".
Blackler was assessed as a high likelihood of reoffending and a very high risk of harm to others.
Justice Dunnigham imposed a minimum non-parole period of three-and-a-half years.
