David James Pye, 43, stood trial in 2025 for the murder of Rebels boss Nick Martin at Perth Motorplex in December 2020.
Pye had hired an ex-army reservist, who cannot be named for legal reasons, to carry out the public assassination.
West Australian Supreme Court Justice Joseph McGrath on Friday found the Rebel-turned Comanchero defector guilty on all six of his charges, including inciting and procuring murder.
These also included Pye trying to arrange for the same shooter to murder his ex-girlfriend and Comanchero boss Raymond Cilli, who lived in Thailand. Their killings never eventuated.
Prosecutors said the case rested on whether the judge accepted the evidence from the trained marksman hired by Pye for the killing.
But Pye's barrister, David Hallowes SC, argued the shooter was a liar and the bikie never asked him to kill Martin.
Justice McGrath said it was obvious the gunman testified against Pye to advance his own interests after he was given a discount on his jail term and was at risk of being re-sentenced to an increased longer term had he not given evidence.
"Having carefully assessed all relevant factors that bear on the credibility and reliability of (the shooter), I find that (his) evidence is both credible and reliable," the judge said in his verdict.
The gunman said Pye first made contact with him through Instagram while he was serving in Iraq with an aid group.
Upon returning to Australia, he met up with Pye to source MDMA for personal use when Pye asked him to kill his ex-girlfriend, which he declined.
The pair met up again a week later when Pye told the would-be assassin he wanted to kill Martin, stating the pair were in dispute over recruitment in the Rebels bikie gang.
Pye said Martin had "ordered a hit on him, and he wanted to put a hit on Nick Martin" and that he "just wanted to blow holes in Mr Martin".
The bikie promised the gunman $150,000 to carry out the hit on his one-time ally, their relationship having soured when Pye defected from the Rebels to the Comancheros.
The shooter was given $10,000 to do reconnaissance on Martin who was tailed to his house and had a drone flown over the property.
He also scoped out Perth Motorplex on two separate occasions.
The sniper, who is serving a 20-year prison sentence after pleading guilty to murder, used a .308-calibre rifle to target Martin 365 metres away while he sat with his loved ones in a spectator area at the racetrack.
The bullet travelled through Martin's body and exited from his lower back before striking another man in his arm, seriously injuring him.
Pye later sent the shooter a message consisting of two coffin emojis and a hand clap emoji.
"One dead, one serious," he said.
The sniper gave evidence at the trial that he only received a total of $90,000 of the promised $150,000 after the shooting, to which Pye replied with words to the effect of "it is what it is".
The relationship between the two bikies featured a level of animosity that the judge described as "hatred", with Pye describing Martin as a "poisonous c***" and that he "wasn't there for the club, he was there for himself".
Martin was said to have a tattoo on his back of a bullet with Pye's name on it.
The convicted murderer will be sentenced at a later date.
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