Unmedicated and sleep deprived, Brown stabbed his 52-year-old sister, Therese Ann Brown, to death in their Bulli home in the early hours of January 3 last year.

The 47-year-old then plunged the knife into his own chest, before driving 70 kilometres to Gladesville where he walked into the police station at 5.30am and notified officers of her death.

It was there the diagnosed chronic paranoid schizophrenic told police that ‘‘it had to be done’’ because people ‘‘were out to get’’ him and his family.

‘‘They are going to get me, they have been after me for a while ... they have cut up other family members in pieces and put them in chicken bags,’’ he reportedly told police.

‘‘I know what was in store for her, it had to be done. They’re coming to get me.’’

The court heard Brown’s delusions involved his finances and the irrational belief anyone pictured in photos displayed in his home would be murdered by the unknown people.

Following the attack, he provided an incoherent version of events to police, revealing he had not slept in three days and had been hearing voices urging him to kill his sister.

Giving expert evidence for the prosecution, forensic psychiatrist Professor David Greenberg said Brown’s delusions led him to believe he was saving himself and his sister by carrying out the violent attack.

‘‘He had paranoid delusions involving his finances and the thoughts that people were going to persecute him or harm him,’’ Prof Greenberg said. 

‘‘He had thoughts the people were going to cut him up into pieces and murder him.

‘‘He didn’t know the act was morally wrong because he was labouring under a defect of reason at that time.’’

After stabbing his sister to death, Brown attempted to self-harm by fixing a knife to a wall and trying to run onto it.

He was treated at Royal North Shore Hospital for a puncture wound to his chest after his contact with police.

On Monday, the court heard Brown had stopped taking his psychiatric medication in the lead-up to the attack, and had been admitted to Wollongong Hospital in July-August, 2013, and again in September-October, 2013, with similar paranoid delusions.

However, Prof Greenberg ruled out Brown’s paranoid fixation on his finances and his reported $40,000-plus debt with the Australian Taxation Office as a motive.

Brown has pleaded not guilty to the stabbing murder of his sister on mental health grounds.

Giving expert evidence for the defence, forensic psychiatrist Dr Richard Furst agreed with Prof Greenberg’s diagnosis that Brown suffered from ‘‘treatment resistant schizophrenia’’ and had a poor prognosis for recovery.

Dr Furst noted Brown was given two types of anti-psychotic drugs while in custody but had not responded to the treatment, even after eight or nine months.

He said Brown would require several years’ treatment in a secure forensic hospital following the court’s decision.

Supreme Court of NSW acting Justice Jane Mathews reserved her decision for a later date.