Susan Couch's victory in the Supreme Court yesterday came with a sting in the tail - the Court has set the bar far higher for her and others to win "exemplary damages".

Her lawsuit against the Corrections Department for contributing to her permanent injuries at the hands of triple murderer William Bell can now go ahead.

But she will have to show that the department and its officers knew their failings in monitoring Bell could lead to an attack and injuries such as those she suffered.

Until yesterday, she would have had to show just that Corrections had been "outrageous" and reckless.

Now, her quest for justice will need to show the department had "consciously appreciated the risk" that releasing Bell on parole posed to her safety and that it "proceeded deliberately and outrageously to run that risk".

Bell, who is serving a 30-year non-parole prison term, had 102 convictions when he attacked Ms Couch during a murderous rampage at the Mt Wellington-Panmure Returned and Services Association club in December 2001 in which three people died.

Ms Couch, who was a part-time accountant at the RSA, was left with brain damage and partial paralysis. She also suffered two breaks to her right arm, a break to her left arm and a fractured cheekbone.

She lost 75 to 80 per cent of her blood and spent six months in Middlemore Hospital, followed by years in rehabilitation.

She still has difficulty speaking and walks with a cane.

In June 2008, the High Court granted Ms Couch leave to sue Corrections for $2.55 million in damages. The department appealed against that decision and won.

Last March, Ms Couch appealed against that decision in the Supreme Court, and yesterday the court overturned the Court of Appeal ruling and also awarded her costs of $27,500.

Her lawsuit, for $500,000, will go to a full High Court hearing expected to start in the next 18 months to three years.

The Supreme Court unanimously held that Ms Couch could take a case for exemplary damages, which cannot be compensation for injury but are, in law, an explicit way of punishing the Corrections Department financially.

The court said that neither accident compensation legislation nor laws covering the liability of government departments and employees could block Ms Couch's case from being heard in the High Court.

But the Supreme Court judges split four to one in raising the standard Ms Couch and others will have to meet to win damages. Chief Justice Dame Sian Elias dissented, strongly opposing the higher threshold.

Ms Couch's lawyer, Brian Henry, said she had "no illusions" that she had a difficult legal battle ahead.

He acknowledged the new standard the Supreme Court had set but vowed he would show Corrections had deliberately contributed to the outcome.

"The negligence had a real deliberateness about it in the sense that it was an ongoing breach. They knew the breaches were there, they knew it was ongoing and they did nothing about it. Deliberate is not a hard point for me to prove because they just didn't do it."

Mr Henry said the Supreme Court decision imposed stricter criteria for claiming exemplary damages.

"They are trying to write down the remedy, that's for sure. It's always easier if the test is an easier one, but in terms of my case, I am not worried about it. We have always said that the deliberate part is there."

Auckland University associate law professor Bill Hodge said that while the ruling was a victory for Ms Couch, a higher standard had been set for her to prove her case against Corrections.

"She can go ahead with her case, but ... the bar has been set much higher than the Privy Council ruling."

Professor Hodge said Ms Couch was going to have to prove awareness or specific awareness of negligence.

"This is a higher standard, but it is certainly better than a complete loss.

"They [the Supreme Court] have said, 'Good luck, you can go ahead, but we are making it more difficult'."

Ms Couch, who burst into tears of happiness when she heard the decision, did not receive a lump sum from ACC but was entitled to $60 a week because she is a solo mother of 11-year-old Jackson, Mr Henry said.

Last night, Ms Couch told Close Up that compensation money was not the main reason for her fight.

"The money's certainly part of it - I'm not going to come out and say it isn't ... There's a lot [of people] out there that think I did and think I'm living large. So it's the money and it's the not wanting for this to happen to somebody else because it has been a struggle."

Ms Couch said she felt sorry for the probation officers, particularly the woman supervising William Bell, because she was not experienced in her job. But she did not hate them.

Garth McVicar, spokesman for the Sensible Sentencing Trust, which has paid Ms Couch's court costs of about $40,000, was in court with her lawyer yesterday when the judgment was released.

"It's about changing the system. Bell was a ticking time bomb, he wasn't rehabilitated, should never have been allowed on parole."