Convicted triple murderer Ian Francis Jamieson doesn't deny he stabbed a neighbour to death before shooting his victim's elderly parents in the head at their homes in regional Victoria.
But he wants to overturn his murder conviction for the fatal stabbing of his Wedderburn neighbour Gregory Holmes because he claims it was self-defence.
Jamieson, 66, appeared before the Victorian Court of Appeal via video link on Tuesday but did not say anything as barrister John Desmond made submissions on his behalf for an appeal against conviction.
Jamieson was last year jailed for life with a minimum of 30 years after pleading guilty to murdering Mr Holmes, 48, and his mother Mary and husband Peter Lockhart.
Mr Desmond says his client has a "subjective belief" he is not guilty of murdering Mr Holmes, who was stabbed 25 times.
This could potentially affect the integrity of Jamieson's guilty plea to Mr Holmes' murder, the barrister said.
"His subjective belief was he was acting in self-defence," Mr Desmond said.
"There is a risk to the administration of justice."
Jamieson repeatedly stabbed Mr Holmes, 48, with a hunting knife on October 22, 2014 following a long-running dispute about a dirt road near their properties.
Jamieson used to have a cordial relationship with the Lockharts until he took issue with Mr Lockhart's use of the road reserve.
Jamieson complained that the use of the dirt road led to dust blowing onto your farm, dirtying his property and polluting his drinking water.
He later told police that after stabbing Mr Holmes, he decided to "sort this out for good" and "clean the other ones up".
Jamieson then went home, loaded two shotguns, and walked to the Lockharts' farm.
He shot 78-year-old Peter Lockhart four times before he reloaded his gun and shot 75-year-old Mary three times.
Jamieson has previously claimed Mr Holmes stabbed him with a syringe containing what was "probably ice" during their struggle.
Justice Elizabeth Hollingworth rejected this claim at sentencing, as did the prosecution at a pre-sentence hearing.
But on Tuesday Jamieson's barrister said the "syringe issue" was a viable defence that Justice Hollingworth should not have dismissed.
Senior crown prosecutor Christopher Boyce SC said Jamieson had received sound legal advice before he decided to plead guilty.
"The allegation of lack of procedural fairness is without merit," he told the Court of Appeal.
Jamieson pleaded guilty to all three murders in April 2016, then unsuccessfully tried to change his plea on the first charge.
Justices David Ashley, Robert Osborn, Joseph Santamaria have reserved their judgment.