A 16-year-old boy who wanted funds to leave home killed his neighbour, robbed him and burnt down his house, a Sydney jury has been told.
Crown prosecutor Terry Thorpe said when the teenager was arrested he was found with $2612 in cash, said to be the proceeds of the robbery.
But the teenager's barrister, Dina Yehia SC, said the boy later disclosed the reason for the killing was that the neighbour had sexually abused him since he was about 10.
The teenager, who cannot be named as he was 16 at the time, has pleaded not guilty to the September 2008 murder of his 64-year-old neighbour, who lived on a semi-isolated property in the northeast of NSW.
In the Crown opening on Monday in the NSW Supreme Court, Mr Thorpe said the victim was stabbed at least twice before being very badly burnt after his house was set alight.
"There is not going to be any dispute that the accused did the act which caused the death of the deceased," he said.
But the defence said the teenager was not guilty because at the time he was suffering from a mental illness.
If the jury rejected this, the next issue involved provocation relating to the alleged sexual abuse.
"The Crown says (the teenager) was motivated by a desire to get money and the deceased was nothing but an unfortunate victim of the accused's plan," Mr Thorpe said.
A third issue related to whether the boy was suffering from "a substantial impairment of the mind" at the time, which would reduce the murder count to manslaughter.
Mr Thorpe said that on the evening before the stabbing, the teenager's parents argued about him and police came to the property.
When the mother got up the next day, she could not find her son but saw a plastic bag containing some of his clothing, which was bloodstained, and items belonging to the neighbour.
She drove to the neighbour's property and found the house had been burnt down.
When police located the neighbour's missing car, they found a blood-stained boning knife inside.
Ms Yehia said it was not in dispute that the teenager stabbed the neighbour at his home, took property and set the house on fire.
But she said he suffered from depression since he was about 12, was on medication and had attempted self-harm.
About six months after the stabbing, the teenager began to disclose the reason for the killing as being sexual abuse.
"I expect you will hear evidence that he did not report it because he was ashamed, embarrassed and felt guilty," she said.
But she said a witness would give evidence that hours after the killing, the teenager said: "F***ing dog ... wanted to molest me and deserves what he gets".
The trial continues before Justice Robert Shallcross Hulme.