Drunk and high on cannabis, a Queensland teenager stole a four-wheel drive looking to score more drugs.
Instead, the learner driver killed an engaged couple and their unborn child, changing their devastated families' lives forever.
A tragedy was "almost inevitable" when the drug-fuelled teen began driving recklessly and dangerously in the stolen Landcruiser, a court has heard.
In the end, it took just 20 minutes before the teen ploughed into Matthew Field and partner Kate Leadbetter, who was six months' pregnant, while they were walking their dogs southeast of Brisbane on Australia Day last year.
The driver, who cannot be named because he was 17 at the time, will be released from custody six years to the day after the horror collision.
"One episode of offending ... resulted about 20 minutes later in the heart-rending death of an innocent young couple," Justice Martin Burns said to the teen during sentencing on Wednesday.
"(The teen) ... drove ... so dangerously over a sustained period ... without any regard for the safety of anyone ... that something like the terrible tragedy which unfolded must be seen to be an almost inevitable consequence."
The teen ran a red light at Alexandra Hills, colliding with a truck before rolling and hitting the couple.
Mr Field, 37 and Ms Leadbetter, 31, were killed instantly, suffering "catastrophic injuries".
Their baby, who was to be named Miles, was delivered stillborn at Ms Leadbetter's autopsy.
The teen fled the collision with minor injuries, stealing keys from a nearby house before being caught by a resident before police arrived.
"They found you lying on the ground crying," Justice Burns said.
The teen later appeared shocked he was responsible for the couple's deaths when interviewed by detectives.
He had been drinking and using cannabis from about 10am that day and had a blood alcohol content of between 0.151 and 0.192 per cent two hours after the crash.
Earlier, he'd gone with a friend to Cleveland to get more cannabis and was found with almost $6000 when arrested.
The teen and friend separated after an argument and he stole the 4WD, at times driving twice the speed limit, on the wrong side of the road and nearly crashing.
He sideswiped one vehicle, did a burnout on soccer fields and was travelling at 102 km/h five seconds before the crash, with his brake lights seen to illuminate moments before the collision.
Justice Burns said taking into account the teen's protracted period of extremely dangerous driving that culminated in a grossly negligent final act, he regarded the manslaughter offences as "particularly heinous".
But the teenager had to be sentenced as a child, with the "grave nature of offending" balanced by his youth.
The sentence was also based on the teenager not intending to kill or do grievous bodily harm.
The teen's upbringing was "marked by significant deprivation and neglect" with his mother being sent for psychiatric treatment and his father to jail, Justice Burns said.
The child safety department intervened when he was aged nine because he was self-harming, left unsupervised, unfed, and exposed to domestic violence and abuse.
At times he used cannabis and up to 1.5 grams of meth every day, was frequently absent from school, sometimes living in parks.
The teenager - who was first charged with murder, but pleaded guilty to two counts of manslaughter and a raft of other charges - stood stony-faced as he was sentenced.
It was in contrast to the victims' families who Justice Burns said had been left with a gaping hole in their everyday existence.
Many family members were in tears but none spoke to media as they left court.
However, they made their feelings clear in victim impact statements read on Tuesday.
"Australia Day will now have a whole new meaning for us. It will be a remembrance day," Matthew's father, Russell Field, said before taking aim at the teenager for his "dog act".
Ms Leadbetter's mother, Jeannie Thorne, described her only child as "the light of our lives, the hope for our future".
"We will never see our girl again, never have grandchildren. Our family is destroyed," she told the court.
Justice Burns sentenced the teen to 10 years in detention, requiring him to serve 60 per cent.
He will be released on Australia Day 2027, at the age of 23.
However, Justice Burns added: "No sentence will be adequate ... (and) can't do justice to the suffering you have caused."
