The vision of her nieces in their child-sized coffins still haunts Evalyn Clow.

Almost a quarter of a century on and the full details of their murders remain too gruesome to be publicly released.

On February 21, 1993, William Patrick Mitchell used an axe to end the lives of Karen MacKenzie and her three children — Daniel, 16, Amara, 7, and Katrina, 5 — at their home in Greenough, 400 kilometres north of Perth.

"You just look at all their photos and you just wonder how anyone could do anything like that, especially to children," Ms Clow said.

Taxing process on victim's families

The house in Greenough where Karen McKenzie and three children were murdered by Mitchell. ( ABC )

Mitchell was convicted of four counts of wilful murder and four counts of sexual assault and handed four concurrent terms of life imprisonment by the state's Supreme Court.

In 2013 he finished serving his mandatory 20-year non-parole term.

Under existing sentencing laws he now has a right to be considered for parole every three years, even if he does not apply.

That process saw Ms Clow contacted by the Victim Notification Register twice in three years as Mitchell's parole was considered by the Prisoners Review Board.

"I don't know what you have to do to be sentenced to jail for life, but it's not killing four people," she said.

"You just start to get into the swing of getting on with life and then everything comes back down on top of you, you have to re-live everything."

"It's a long process and it's very taxing on family situations and causes a lot of grief."

Government set to amend laws

Catherine Birnie when she was taken into custody over the murder of four women in Perth, 1986 ( ABC News )

WA Attorney General John Quigley wants to avoid the trauma of ongoing parole appeals.

Mr Quigley is proposing to amend WA's parole laws to give the Attorney General the power to tell the State's Prisoners Review Board not to consider parole for Mitchell, and killers like him.

"I want to introduce legislation to this effect that where we have a mass murderer — which will be defined as a person who kills more than two people on one day, or two or more people on consecutive days — then the Attorney General of the day can write to the Board and tell it not to consider that mass murderer for parole during that Attorney General's tenure," he said.

The proposed changes were born out of an online campaign created by Kate Moir in early 2016.

She was the sole survivor of serial killers David and Catherine Birinie, who in 1986, murdered four women aged between 15 and 31.

In an online petition, which carries more than 40,000 signatures to date, Ms Moir called for mandatory parole hearings for murderers in the State to be revoked, and parole legislation to be overhauled Australia wide.

"Last year, Kate Moir, a woman who was a victim of Catherine and David Birnie, approached me very distressed over the pending consideration of parole for Catherine Birnie," Mr Quigley said.

"What she said is every three years Catherine Birnie is reconsidered for parole and at that time the board write to her for her views and she's got to write through the whole trauma again as she sets out her traumatic circumstances for the boards consideration.

Changes due by 2019

The Government expects the legislation to be tabled within 18 months.

WA Attorney-General John Quigley ( ABC News: Kate Lambe )

Mr Quigley said if the laws were changed, it could be up to eight years before Mitchell or Birnie were again considered for release.

"They (the families of victims) can put this in the bottom drawer and forget about it because I as Attorney General will not be releasing that murderer," he said.

"I will not have the victims going through this trauma.

"They have suffered enough already, they don't need this every three years."

The State's former Attorney General Michael Mischin met with Ms Moir in April last year.

After the meeting he told Ms Moir and local media he was open to the changes, and would seriously consider the request.

Politicising the process

However, in a meeting in February this year Mr Mischin informed Ms Moir the then-Barnett Liberal Government would not be changing the parole laws.

"I have enormous sympathy for those who have survived these people, for those that have been killed by these people and also for the family and friends of those who have been killed by these people.

"But you cannot base a criminal justice system around considerations that only focus on the victim.

"If the court had sought it fit or appropriate to sentence on the basis of no release it could have done so in at least one of those cases.

Western Australia's Shadow Attorney-General Michael Mischin. ( ABC News: Michael Mischin )

"It's altering the scheme under which these prisoners were sentenced quite radically."

He said the Government's proposal would politicise the judicial process.

"Simply to pick isolated cases and say 'I don't want to consider this and I'm going to hand the problem off to someone else', that I think is wrong and that does politicise the process, rather than leaving it as a proper administration of justice," he said.

Ms Clow said the if the proposed legislation was passed she would be able to find peace for the first time in years.

"You don't forget, you can't forget and you always wonder what they would be like and how everything would be," he said.

"But just to be able to have the relief of not doing this every three years, it would be such a weight lifted."