A Perth pensioner who stabbed his son to death, then watched the AFL grand final while two of his other children buried the body in the backyard of the family home, has been jailed for at least 18 years.
Ernest Albert Fisher, 67, was found guilty after a Supreme Court of WA trial last month of murdering Matthew Kyle Fisher-Turner, 23, in October 2016.
Joshua Douglas Fisher-Turner, 28, and Hannah Jayde Fisher-Turner, 21, were both convicted of being accessories to murder.
Fisher argued self-defence, claiming his outgoing, gym-loving son was violent and abusive, particularly towards him, describing him as "like a terrorist".
The court heard the family had been dysfunctional and unravelled after the death of its matriarch in 2014.
The final straw for Fisher was when Matthew insisted on borrowing his car, which triggered an argument because he wanted to drive to friends to watch the AFL grand final on TV.
After piercing Matthew's lung and aorta with knives bought specifically for the killing, Fisher started digging a grave in the rear garden of the Parmelia home.
He then left the house to watch the match, leaving it up to Joshua to bury his brother, while Hannah helped carry the body outside on a ladder.
Both cleaned up the crime scene.
When friends became concerned about Matthew's sudden disappearance, Fisher claimed his son was "over east with a chicky babe", but they were unconvinced and contacted police.
Fisher initially maintained the story when interviewed by detectives.
But after about 90 minutes of questioning, he admitted he'd killed Matthew four weeks earlier, told them where his son was buried and called him a "complete and utter arsehole".
Justice Stephen Hall said he accepted there were confrontations and disputes, but whatever violence occurred was not of the severity or frequency to justify Fisher's actions.
Justice Hall said there were "obvious alternative ways" of dealing with it.
"You did not act out of fear but out of hatred, frustration and anger," he said.
Justice Hall said Fisher had shown no regret or remorse, noting he told police the sensation of killing his son wasn't pleasant, but also remarked he'd "done the right thing" and continued to say derogatory things about Matthew.
The judge described Fisher's reasoning and actions as disturbing and callous.
"Having done the unthinkable, you were apparently not emotionally affected," Justice Hall said.
"It is also reprehensible that you chose to involve Joshua and Hannah."
In a letter to the judge, Hannah said the events of that day filled her heart with pain and sadness, and haunted her.
Joshua sobbed as he was sentenced to a maximum of four years in jail, while Hannah was handed three years and eight months.
With time already served, Hannah will be eligible for parole at the end of this month while Joshua could be released in late October.
All three have been in custody since late October 2016.