NSW teen 'went black' and killed neighbour

·3-min read

Billy Krey was four years old when he began "stabbing motions" and the knives were hidden away.

His blackouts were rare, but one of the last times he experienced "black mode," he fatally plunged a knife into his neighbour, the NSW Supreme Court was told on Wednesday.

At 19 Krey followed and stabbed father-of-seven Ioakima Sini 16 times outside his home in Whalan in Sydney's west, on July 15, 2017.

Krey plead guilty to manslaughter and was deemed substantially impaired by abnormality of the mind and sentenced to at least six years and six months in prison by Justice Mark Ierace.

While Mr Sini had engaged with him first "the offender's response was so disproportionate that I find the attack was unprovoked," Justice Ierace said.

Krey's childhood of extreme deprivation and significant mental disorders - foetal alcohol syndrome, intermittent explosive disorder and complex post-traumatic stress disorder - contributed to the offence, the judge found.

"Without them, the attack would not have occurred," Justice Ierace said.

"The attack was explosive, random and inherently lethal in nature."

Mr Sini's eldest daughter wrote a statement on behalf of her siblings of the profound impact of losing their father.

Krey had been living with his mother when he awoke at 4pm "in a bad mood or something" he told police soon after the attack.

After accusing his mother of stealing $50 and threatening to stab her, she left and briefly spoke to Mr Sini.

He then walked over to Krey still inside the home and yelled out to him before leaving.

Moments later several witnesses watched the teenager follow and confront the neighbour outside, repeatedly stabbing him until he crumpled to the ground.

Mr Sini had four times the legal driving limit of alcohol in his system which "may explain why he was unable to react defensively by running away, fighting back or calling for help," the court was told.

Krey immediately walked to his grandfather's telling him "I think I hurt someone," before police arrived and arrested him.

At the station, he asked detectives: "The person I stabbed, can you tell me anything about him?"

He explained he always carried a knife when walking to protect him from the "boys" who tried to rob people around their neighbourhood, but then his neighbour started yelling at him.

"That ticked me off and like everything just went black."

His early experience of "severe childhood abuse and trauma," was laid out in multiple specialist reports.

Growing up he experienced "extreme domestic violence," involving his father who was jailed for attempted murder.

His mother was drug and alcohol addicted while pregnant, and by the age of 15, he had been moved around 16 different placements and continues to suffer from intellectual impairment.

The pre-schooler would light fires, punch family members, "climb the roof" and was deemed extremely hyperactive and diagnosed with ADHD.

Visitations with his mother during foster care resulted in markedly deteriorating behaviour immediately after, improving when their contact was limited.

After living under the supervision and care of his grandfather he moved back in with his mother and stopped taking his medication that had a calming influence on him, according to multiple reports.

Following the attack, one treating doctor found Krey "expressed seemingly genuine regret and remorse".

His prospects of rehabilitation were dependent on the long-term treatment he would need but could be positive, the judge found.

Krey has been jailed for a maximum of 11 years and granted special circumstances with a lengthy parole period to allow a program of treatment to address his mental conditions.

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