JURORS in the double murder trial of 28-year-old Nicolau Fransisco Soares have retired to consider a verdict.
Mr Soares is accused of killing his mother Dr Delys Weston and step-father Professor Gavin Mooney in Decemer 2012.
He has pleaded not guilty by reason of insanity.
The jury has heard Mr Soares had been living with schizophrenia since as early as 2006.
Evidence was given that his paranoid beliefs and grandiose delusions penetrated "almost to the core of his existence" at the time of the attacks.
In her closing address, defense lawyer Rochelle Mainwaring said there was no dispute Mr Soares was responsible for the physical act of killing the couple.
But Ms Mainwaring said her client was not able to understand or appreciate what he was doing was wrong.
"The devastating outcome was, for Mr Soares in his mind, just a means to an end," Ms Mainwaring said.
Crown prosecutor Linda Mason said arriving at a verdict of not guilty by insanity was not a soft option.
"The state does not urge a verdict other than that raised by the defense - that is to find Mr Soares not guilty by reason of insanity," Ms Mason told the jury.
"As gruesome as the killings were, perhaps that is the best insight you will get into the mental state of Mr Soares at the time," she said.
MORE TO COME