The teenage boy who fatally injured pregnant woman Diane Miller by throwing a piece of concrete at her in a suburban Perth car park has been sentenced to five years in juvenile detention.
WARNING: Aboriginal and Torres Strait Islander readers are advised that this article contains an image of a person who has died, used with the permission her family.
The 17-year-old, who cannot be named due to his age, was initially charged with murder but later pleaded guilty to manslaughter.
Ms Miller died days after the teen threw the 1.9-kilogram piece of concrete that hit her in the head as she sat in a car on November 29 last year.
Minutes before, the 30-year-old had been trying to defuse an altercation between her partner and a group of youths outside a Karawara car park.
The court was yesterday told Ms Miller's partner had accused the group of throwing something at his car, while the youths believed the car occupants had yelled racial slurs at them.
Ms Miller's sister, Alison Miller, sunk to the floor in the public gallery when vision of her "baby sister" was played in court, while other family members were seen screaming and crying after the sentence was handed down.
The vision showed youths arming themselves with stools, bottles and other objects.
Some members of Ms Miller's group pleaded with the teenagers to stop fighting, saying there was a baby and a pregnant woman in the car.
The melee was all but over when the teenager, who had been hiding behind a brick wall, threw the rock into Ms Miller's open passenger window.
Boy 'threw rock without thinking'
Prosecutor Clare Cullen described the injuries caused to Ms Miller as "catastrophic". She and her unborn child died three days later.
The court was told the teenager became distressed after he learned someone had been injured, saying: "What have I done? What was I thinking? I think I killed a kid."
Defence counsel Kate Turtley-Chappel said the boy had only intended to break a window or hit the car.
"He threw a rock without thinking and ultimately it ended in the loss of a human life," she said.
The boy has been in custody since he handed himself into police not long after the incident in late November, with the court told he had since received threats over his offending.
Ms Turtley-Chappel said the teenager wanted to serve his sentence at Banksia Hill Detention Centre and was likely to receive support for his treatment needs in custody.
Sister grieves over life cut short
The court was told the conditions at Banksia Hill were "very bad" due in part to chronic staff shortages.
Though not involved in any critical incidents while in detention, there have been 45 days in which the teen spent more than 20 hours in his cell due to lockdowns.
In her victim impact statement, Alison Miller described her sister as the "golden child" of the family.
The nickname of "dinosaur" stuck even after her childhood fascination with the prehistoric beasts faded.
Alison Miller's statement said the young mother's life "was just starting to take off" when she died.
Diane Miller's baby, whom she had intended to name Leroy, was due to be born on April 10.
'Triple tragedy': judge
Children's Court president Hylton Quail told the boy he would have to live with the consequences of his actions for the rest of his life.
Judge Quail described the incident as a "triple tragedy" that took the life of the "completely innocent" Ms Miller, deprived her one-year-old son Lloyd of a mother and deprived her unborn child the chance of life.
But he accepted the teenager was not intending to hit someone with the concrete.
Judge Quail said he was satisfied the boy was just trying to hit a window or car door as the vehicle drove past, but also noted "a reasonable person" would have known such an action could have serious consequences.
He found the teenager's diagnosis of foetal alcohol spectrum disorder contributed to his "impulsive" decision to throw the rock at Ms Miller's car.
Judge Quail also accepted the teenager's remorse as genuine, with the boy saying in a letter to the court that if he could swap places with Ms Miller, he would.
He must serve 26 months of his sentence before he is eligible for supervised release.
Family disappointed
Speaking outside court, Diane Miller's brother, Malcolm Clifton, said the family was disappointed by Judge Quail's decision.
"Now Lloyde's going to grow up without his mum, and he had the best mum in the world. She got taken away and all he gets is five years?
"He should've got 15 so he can think about what he's done," he said.
Alison Miller said she felt her sister had been let down by the justice system.
"Justice didn't serve us right today. My sister was harmless, the judge even said it, but the sentence he gave today wasn't fair," she said.
"[The offender] can walk and breathe, he can do what he wants. We've got to go to a grave.
"Still today I get traumatised when I think about my nephew."
