The NSW Government has passed a bill to alter the language of the verdict from 'not guilty by reason of mental illness' to 'act proven but not criminally responsible'.

The change is among the forensic mental health reforms to better reflect community expectations about acts committed by people with mental illness and cognitive impairments, Attorney General Mark Speakman said.

"It can be particularly painful for victims and their loved ones to hear that a defendant is 'not guilty' of an offence, even though the court found the defendant committed the act," he said.

But, for people like Wendy Robinson the bill's wording is not what homicide victims wanted.

Her brother Scott Settree admitted to killing their parents Margaret and Ian Settree in their Cobar home on December 3, 2014 following an argument over a $40 bottle of wine.

The court heard he took a pump action shotgun from his bedroom in the house he shared with his parents and shot his mother in the neck, he then reloaded the weapon and shot his father twice, in the chest and head.

Court documents show Settree told investigating police that he had a "sensation of relief" after the shootings.

The court also heard Settree suffered from schizophrenia and as such was found not guilty by reason of mental illness.

Speaking to the Daily Liberal the day after the bill passed, Ms Robinson said the wording of the verdict makes all the difference and she has accused Mr Speakman of rushing the bill through parliament and not listening to homicide victims.

The wording the victims wanted to see in the verdict was: Act proven by reason of mental illness.

"The act has been proven in the court system and we're identifying that they have been diagnosed with a mental illness," Ms Robinson said.

"Not guilty and not criminally responsible still diminishes their responsibilities of what they've done.

"It's heartbreaking when you've had family members, loved ones or it could even be a friend murdered by a person and there's absolutely no responsibility for what they've done. It just rips your heart in half.

"Society needs to know about their mental illness and the act that they have done has been proven in the courts.

"I have not doubt in my my mind that my brother had a mental illness ... but it's not an excuse to get away with killing people."

Ms Robinson said there are other "loopholes" in the law that need changing, including that people like her brother will have no criminal record if he is ever released.

"If a policeman was to pull him over and do a check on him nothing shows up," she said.

Ms Robinson said this should be changed "for the safety of society".

"My brother, for example, has threatened other people with his violence including other family members and he's quite capable of killing again," she said.

Also, when it has been proven in court that the accused did the act, that they should then forfeit their rights to an inheritance at the time of sentencing.

Settree was initially set to inherit half of his parents' multi-million dollar estate and it was only after Ms Robinson fought it in court that the judge reduced the amount to $100,000 which is being held by the Public Trustee.

"I felt like my brother had been rewarded for killing Mum and Dad, it was a horrible feeling," she said.

"I could not believe that any judge would award money to a killer."

Ms Robinson said her life has changed dramatically since that night in December 2014 and she often feels immense loneliness.

"Even though I'm in a small community where I know everyone, I'm very, very lonely because there are so many memories here of Mum and Dad. I eventually want to leave," she said.

"I don't feel like I have the same happiness in my heart."