Clinton Beau Wrigley, 40, was found guilty of murdering 58-year-old Joel Carter at a rural property in January 2023 after a trial in the NSW Supreme Court.
He attacked the sleeping farmer with a rubber mallet and beat him until his skull was partially caved in at his property near Nyngan in central NSW.
Mr Carter's body was found lying on a metal-framed bed in his lounge room in an advanced state of decomposition two days later.
Wrigley stole the dead man's tools - to sell later - and his Toyota Hilux, which he set on fire in the bush along with his bloodied clothes and the murder weapon.
He decided to murder Mr Carter when he overheard the farmer discussing a plan to exclude his recently bereaved sister-in-law from the farm business, Justice Mark Ierace said.
As a man who had lost his partner to sudden death not long ago, the conversation resonated with Wrigley who became motivated by feelings of anger and disgust towards Mr Carter.
In a covertly recorded call, the farmhand told an acquaintance that the "main thing that done" Mr Carter was his poor treatment of his sister-in-law.
Wrigley formed a "bizarrely moralistic explanation for his extreme violence" which rendered his offences more serious, Justice Ierace found.
The court was told he bragged to multiple people about beating Mr Carter to death, telling one: "I didn't lose no sleep over (Carter). He deserved that."
"He expressed satisfaction for having killed the deceased who, in his mind, morally deserved to die," Justice Ierace said.
He found Wrigley's mental state in justifying such extreme violence was facilitated by his impaired executive functioning, childhood exposure to violence, drug use, and the loss of his wife.
The factors reduced his moral culpability but his prospects of rehabilitation were guarded, especially given he was serving five community sentences at the time.
Justice Ierace sentenced Wrigley to 23 years and nine months behind bars for the murder, and four years and eight months for the thefts and arson offences.
He will be eligible for parole in 2041.
After learning his sentence, the farmhand swore loudly.
"F***ing 23 years," Wrigley exclaimed after the court adjourned.
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