The killer, who cannot be named because he was aged 17 at the time of the offences, fatally stabbed Emma Lovell in the heart after he broke into her family's house north of Brisbane about 11.30pm on Boxing Day in 2022.
Ms Lovell was fatally stabbed during a struggle on her front lawn, with her husband Lee wounded.
The home invasion became the catalyst for "adult crime, adult time" changes in Queensland law under the Liberal National government after it won the 2024 state election.
The new legislation allows for youth offenders to face a mandatory life sentence for serious offences such as murder, with a minimum of 20 years before parole.
The teen was jailed for 14 years with the Court of Appeal reducing his minimum sentence by 18 months in 2025.
The High Court overturned that reduction on Wednesday.
Attorney-General Deb Frecklington had appealed against the sentence reduction, saying the offender could be released before Ms Lovell's two daughters "even get to walk down the aisle".
The High Court justices found the original sentencing judge was correct to not recognise "special circumstances" for the teen when handing him a minimum nine years and nine months.
"There was nothing about the factors of (the teen's) early pleas of guilty, his deprived upbringing, and the positive signs of his ability to rehabilitate that means that it was unreasonable or plainly unjust for the sentencing judge not to reach a conclusion of special circumstances," the High Court's decision stated.
"Indeed, as the sentencing judge observed, the early pleas of guilty by ... (the teen) ... were made against the background of an overwhelmingly strong Crown case".
Queensland Supreme Justice Tom Sullivan in May 2024 sentenced the teen, then aged 19, to a maximum of 14 years with a requirement to serve 70 per cent of that time in detention, after he found the crime to be "particularly heinous".
Following a successful state appeal in August 2025, the teen's minimum sentence was reduced by about 18 months.
Justice David Boddice found the 14-year sentence should stand but reduced the detention period to 60 per cent.
He cited the teen's guilty plea, "genuine remorse and prospects of rehabilitation" as special circumstances justifying his release from detention after serving less than the statutory 70 per cent.
The teen had less than five years left to serve in detention after 500 days of pre-sentence custody in May 2024 were recognised as time served.
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