A Sydney man who was jailed for 35 years for killing decorated New South Wales policeman Bryson Anderson has lodged an appeal against the length of his sentence.

The NSW Supreme Court has been told additional evidence, including a psychiatric report, will be presented at Mitchell Barbieri’s appeal hearing on June 21.

He pleaded guilty to murdering Detective Inspector Anderson, who was stabbed during a stand-off at Barbieri’s rural Oakville property in north-west Sydney in December 2012.

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Two years later, Barbieri was sentenced to 35 years in prison with a non-parole period of 26 years.

The killer’s mother, Fiona Barbieri, was handed a 10-year sentence for manslaughter, with a non-parole period of six years and six months.

Members of Detective Inspector Anderson’s family were in the Supreme Court today to find out when Mitchell Barbieri’s appeal will be heard.

Outside court his brother, Warwick Anderson, thanked the media and the public for their interest.

“Obviously we are going to take a very close interest in this case at every step of the way,” Mr Anderson said.

“Bryson can’t be here, so we are going to make sure that his interests are protected and represented.

“As a family we’re looking forward to the end of it.”

During the sentencing in December 2014, the NSW Supreme Court was told Mitchell and Fiona Barbieri had barricaded themselves inside their home after a violent dispute with their neighbours.

Detective Inspector Anderson was one of the police officers called to the address.

Mitchell Barbieri, now 23 years old, pleaded guilty to stabbing the veteran officer several times with a 15-centimetre hunting knife as he was trying to negotiate with the mother and son.

The fatal wound penetrated 14 centimetres into the officer’s right lung, critically injuring him.

Fiona Barbieri then came out of the house swinging a sledgehammer, according to police witnesses.

Detective Inspector Anderson died at Hawkesbury Hospital later that afternoon.

In 2011, the NSW Parliament passed a law so that anyone found guilty of killing a police officer would be given a mandatory life sentence, but the crown did not pursue that for Mitchell Barbieri because he was affected by his mother’s schizophrenic delusions at the time of the attack.

– ABC