Thorn stood trial for murder alongside two other men, Jordan Bottom and Rikki Smith, for the murder of Mr Lyons in a remote part of eastern Victoria in December 2018.
Mr Lyons was beaten and tortured before he was thrown in a shallow grave, shot in the head, and buried.
Thorn alone was convicted of murder, while Bottom and Smith were acquitted of the more serious charge in favour of kidnapping and assault offences.
The fact only Thorn was found guilty of murder doesn't mean the jury was satisfied that he was the one who fired the fatal shot, Thorn's barrister James Anderson told a pre-sentence hearing in the Victorian Supreme Court on Friday.
"The fact that one was convicted and two were acquitted doesn't mean, as a matter of logic, that Thorn was the person who pulled the trigger," he told Justice Andrew Tinney.
"We say there's insufficient evidence to draw an inference as to who pulled the trigger."
Jurors heard Mr Lyons was set upon by four men in balaclavas - including Thorn and Smith - and beaten with fists and a metal pole until he bled.
He was then tied up and thrown into a car boot where he was trapped for hours while his attackers plotted their next move.
Mr Lyons was then tortured by the men, who wanted him to confess to allegations he sexually assaulted children.
He was locked inside the boot again and driven by Thorn, Bottom and Smith to Double Bridges, where he was placed in a shallow grave and shot dead.
Prosecutor Ray Gibson KC pointed out that Thorn, 57, had confessed to one of his own children that "I killed a man last night".
"Had (the jury) been satisfied Smith or Bottom fired the gun they would have had no option, it would seem, but to find either of them guilty of murder," he said.
Justice Tinney noted a mountain of evidence pointing to Thorn being in the thick of the vigilante plot to kill Mr Lyons, over allegations he had abused children.
"There were a number of important people in this enterprise, but he's at the heart of it," he said, pointing out that his property was the venue for the torture and that he was present in planning talks.
He also noted Thorn's mother's car was used to transport Mr Lyons, the shotgun and shovel to Double Bridges, where Thorn was also present for the the digging of the grave, the shooting and Mr Lyons' burial.
Mr Gibson said it would be open for Justice Tinney to impose a life sentence on Thorn for his crimes, described as the calculated and premeditated killing of a man who must have had the realisation his end was imminent.
He said it was interesting to reflect that Thorn, who didn't even know Mr Lyons, had done so on the basis he wanted to protect children, but had caused the opposite.
The impact on Mr Lyons' own children, three of whom were under 10, had been nothing short of tragic, Mr Gibson said.
"It highlights the very evil of vigilantism," he said.
Justice Tinney has indicated he will sentence Thorn separately to Bottom and Smith, all at a later date.
