Stephen Williams, the man serving a life sentence for the murder Coral-Ellen Burrows, has tried to kill again.

The man serving a life sentence for the murder of Featherston child Coral-Ellen Burrows in a P-fuelled rage has tried to kill again.

His only regret, he told a court, is that he failed.

It was 2003 that Stephen Williams bashed his six-year-old step-daughter to death with a tree branch, in a fit of manic fury. Eleven years later, at Northland's Ngawha Prison, he sharpened a toothbrush, grabbed an inmate in a headlock and stabbed him repeatedly in the face and the neck.

But for the intervention of a prison guard, the stabbing would have taken his family's murder tally to five. Already, Williams, his sister and his parents have been involved in four slayings – and the killers have all been Williams family members or their equally brutal lovers.

Coral-Ellen Burrows was murdered by Williams, infuriated because she wanted to return home from school to fetch a gift she had made for Harold the Giraffe, a visiting anti-drug mascot. Williams, a P-smoker with 89 convictions, viciously beat her. He delivered a killing blow with a tree branch.

Two years later, his sister, Anamari Stone was convicted of manslaughter after she stabbed her partner in the leg with a knife. He bled to death.

Williams' father – a man described as "unbelievably violent" – was killed by his second wife in Australia. She pleaded provocation and was not convicted.

His mother, Robyn Williams, was befriended by Alfred Benning in 1977, who hired her as a housekeeper. His wife went missing and she called police. They found Elizabeth Benning cut up in six pieces, buried in a hole beside a newly planted apple tree.

In the latest incident to darken the violent cloud over the Williams family, the killer's callousness was labelled "reprehensible" by Judge Pippa Sinclair.

In a pre-sentence report prepared ahead of his November 2014 at the North Shore District Court, Sinclair noted to Williams he said he was "disappointed you had failed to kill him".

"You explained to the report writer that you intended to kill your victim, and that your offence was pre-planned to ensure that you received a voluntary directed segregation status so as to be alone and to avoid having to mix with other prisoners," Sinclair said.

"You either made or obtained a sharpened toothbrush to use as a weapon, wrapping a torn sheet to provide a handle. You prepared and packed your belongings knowing you would be transferred to a different area of the prison.

Williams was sentenced to a further five years and eight months, to be served alongside his current life sentence. He has a minimum parole period of 17 years, and will be eligible to appear before the board in 2021.

Coral-Ellen's father, Ron Burrows, said the sentence was not enough.

"If [the sentence] had been implemented from the time he would be eligible for parole then I wouldn't have to go to a parole hearing in six years time ... He nearly killed somebody and he got nothing for it."

On Saturday, Justice Minister Amy Adams launched a new victims code to support victims of crime to make their experience with the justice system "as stress free as possible".

Adams said the code would explain what support services were available to victims

But Ron Burrows said it was "a little too late". The family were left in the dark about Williams' latest offending, informed only once they were belatedly placed on the victim impact register last week.

As for Robyn Williams, she died two years ago with her son and daughter 's prison sentences hanging heavy over her. She told a close friend: "I think that I'm one of God's experiments. I think God wants to know how much pain a human being can actually take and I'm the experiment."