A Narromine man cut a crucifix into his brother’s body with an axe after strangling him because they were “fighting in the afterlife”, a Sydney judge has heard.

Wayne Michael Spillett, 42, yesterday pleaded not guilty in the NSW Supreme Court to murdering his younger brother, Mark Spillett, last August.

At the time of the incident Orana Local Area Command crime manager Detective Inspector Mick Willing said it appeared as though the deceased was “struck by a number of blows with an implement we believe was an axe”.

Wayne Spillett’s lawyer, John Stratton SC, urged that his client, who has struggled for a number of years with bipolar disorder, be found not guilty on the grounds of mental illness.

Mark Spillett’s charred remains were found in a burned-out cottage on a property the brothers shared in Narromine.

It is believed the blaze probably started about two days before the remains were found.

Experts were flown in from Sydney to examine the scene of the blaze and the body was found in the house.

An autopsy revealed the 39-year-old drill worker had been throttled and the figure of a cross cut into his body.

Prosecutor James Barnett told the court Mark Spillett had also been struck over the head with a blunt object.

Wayne Spillett fled north to the town of Manilla, where he confessed to his mother and other family members that he was responsible for his brother’s death.

Detailing the case against Spillett, Mr Barnett said he appeared to be descending into mania in the weeks before the murder, telling his children he had been drafted to fight in the “covert land army”.

His treating psychiatrist, Lisa Brown, told Justice Howie that Spillett suffered persistent paranoid delusions, including that he was being stalked by the Ku Klux Klan and various bikie groups.

On the night of the murder, Mark Spillett told friends at the Royal Hotel, where he’d been drinking, that he was “going home to sort out my crazy brother”.

Mr Barnett said Mr Spillett’s friends described him as a “gentle giant”, and he was the only one in the family who could handle his older brother when he was manic.