Mother and son who killed decorated NSW detective 'tried to email Putin'

A mother and son who killed a police officer during a siege at their NSW rural property tried to contact Russian President Vladimir Putin about their "plight", a court has heard.

The full details of the events that led up to Detective Inspector Bryson Anderson's death were revealed today during a sentence hearing of 47-year-old Fiona Barbieri and her 21-year-old son Mitchell.

The Supreme Court heard the pair had been embroiled in a long-running dispute with their neighbour Kevin Waters at their rural Oakville property in Sydney's northwest.

Crown prosecutor Mark Tedeschi QC said that by December 6, 2012, the relationship had deteriorated to such an extent that Mr Waters began installing flood lights on his property.

Fiona - swinging a baseball bat - and Mitchell - armed with a crossbow - went up to the two electricians installing the lights.

Mitchell fired two arrows, narrowly missing them, Mr Tedeschi said.

As the first police arrived at their property just before 2.30pm, the court heard the Barbieris holed themselves up inside their home.

Here they sent an email to a number of politicians, including Tony Abbott, Joe Hockey and Vladimir Putin, saying: "We have every right to defend ourselves, our family and our property."

Det. Insp. Anderson tried a number of times to get Mitchell to come outside but eventually the order was given to kick the door in.

The decorated officer was stabbed twice by the then 19-year-old, once in the cheek and fatally to the chest, Mr Tedeschi said.

On the morning they were due to stand trial at the NSW Supreme Court last week, Mitchell pleaded guilty to the officer's murder while his mother pleaded guilty to manslaughter on the grounds of substantial impairment.

The court heard Fiona was suffering from paranoid schizophrenia at the time of the siege and that her delusions had been transferred to her son.

Due to this cognitive impairment, Mr Tedeschi said the 21-year-old would not be subject to the mandatory life sentence reserved for people who murdered police officers.

The matter will return to court later this month.