A boy on a good behaviour order for drunkenly crashing a stolen car "thought he was invincible" when he again got behind the wheel and hit a tree at 200kmh, killing two girls who were "callously abandoned to die".
It can now be revealed the 17-year-old boy, who had been trying to impress the victims, was also on bail for carjacking a taxi driver when he killed Claire Sankey, 15, and Susi Kopysiewicz, 14.
Details of the killer's crimes were canvassed in the ACT Supreme Court during a sentence hearing on Monday.
He had previously pleaded guilty to eight charges, including two counts of culpable driving causing death.
Court documents show the killer, who cannot be named because of his age, joined forces with another juvenile to steal a car in January 2022.
The pair botched an attempt to carjack a woman in Monash before taking a taxi from its driver, who was giving them a free lift, at knifepoint in Gowrie.
In October 2022, while on bail in relation to that incident, the killer had 12 stubbies of beer at a friend's home on a Saturday night.
When he returned home, he drank about half a one-litre bottle of rum.
In the early hours of the next morning, when his bail conditions required him to stay home, the killer took the keys to his mother's Toyota Camry and drove off in it with another boy.
After picking up Claire and Susi, he headed for the Monaro Highway and drove north.
On that road, traffic cameras clocked the unsupervised learner travelling at 200kmh seconds before he ultimately crashed in Hume.
It had been raining and the vehicle lost traction on the wet road, causing the car to spin and crash through temporary construction fencing before smashing into a tree so hard it broke off at the trunk.
After striking a second tree, the car came to rest and both boys ran away.
The wreckage lay hidden in trees by the road for several hours before a passing motorist spotted it and alerted police.
Officers who attended the scene found both girls, who had missed repeated calls from the killer, dead in the vehicle.
After being arrested a few hours later, the killer told investigators he thought the girls had escaped the wreckage.
'Light of our lives'
On Monday, Claire's sister, Nora Lal, told the court the victims had been best friends.
She described how her whole life had changed when she received a phone call about the death of Claire, who was "the light of our lives".
"Now, it's been nine months since we've lost her and I still feel as lost as the day I received that phone call from my dad," Ms Lal said.
"I now bring grief with me in every experience I have."
'Rank selfishness'
In written submissions tendered to the court, the acting ACT Director of Public Prosecutions, Anthony Williamson SC, said the boy had ignored repeated warnings from both girls to slow down.
Mr Williamson said the boy would have been sleep-deprived as well as intoxicated, having admitted using cannabis and MDMA during a multi-day "bender" before the incident.
Autopsy reports revealed the crash did not kill either Claire or Susi instantly, but both girls would almost certainly have died regardless of whether they received medical attention.
Mr Williamson took aim at the killer's decision to flee the scene, writing that the girls had been "callously abandoned to die" in an "undignified" manner.
"The prosecution submits that the offending ... is redolent of the offender acting out of rank selfishness and self-interest at the expense of his victims," Mr Williamson wrote.
"The surviving passenger ... suggested that they ring emergency services, but the offender refused to accede to that suggestion."
Killer 'an exemplary prisoner'
Defence lawyer Edward Chen said his client, who has been remanded in custody for the past nine months, acknowledged the "devastating" impact of his "foolish" decision to drive.
Mr Chen told the court the 17-year-old had been "an immature boy who thought he was invincible".
It was unfortunate, the Legal Aid lawyer said, that it had taken a tragedy of this magnitude for the teenager to be "jolted into behaving maturely".
But Mr Chen said that was what had occurred, telling the court the boy had been "an exemplary prisoner".
He noted the boy had, through his mother, contacted ACT Attorney-General Shane Rattenbury in the hope of becoming the face of a campaign to curb reckless driving.
Mr Chen ultimately asked Justice David Mossop to impose a sentence that would soon result in the boy leaving the Bimberi Youth Justice Centre, arguing there was "little utility" in keeping him behind bars.
Justice Mossop indicated he planned to sentence the boy on Wednesday.
