The juvenile offender who brutally murdered mum Emma Lovell in a Boxing Day home invasion has launched a shock appeal, arguing the 14-year sentence he received is “manifestly excessive.”

Now 20, the man admitted to stabbing the North Lakes mother-of-two in the chest during a violent break-in at her family home in 2022.

He had previously pleaded guilty to murder, armed burglary at night, malicious act with intent, and assault in company causing bodily harm.

Know the news with the 7NEWS app: Download today

At sentencing last year, Justice Tom Sullivan handed down a 14-year youth detention order, well above the usual 10-year maximum under Queensland’s youth justice laws.

He cited the teen’s “particularly heinous” conduct, which included stabbing both Emma and her husband Lee and kicking Lee in the head after he was wounded.

“This offending was atrocious and would create outrage in the community,” Justice Sullivan said at the time.

A teen who murdered a mother of two during a home invasion is appealing his sentenced to 14 years. Credit: AAP

Now, the killer’s legal team is seeking to have the sentence reduced, claiming the judge erred by ruling the crime met the threshold for an extended sentence, and that not enough weight was given to the teen’s early guilty plea.

The appeal has left Emma Lovell’s widower, Lee Lovell, and their two daughters, Kassie and Scarlett, devastated.

“So if they take that away, it’s like putting less value on Emma’s life,” Lee told 7NEWS.

“The best I can hope for is that they’re gonna uphold the 14 years.”

The appeal follows a controversial earlier decision in which the other teen co-accused was acquitted of both murder and manslaughter — despite participating in the same break-in.

The Lovells were attacked in their home north of Brisbane at about 11.30pm on Boxing Day.

Emma Lovell was killed during a home invasion on Boxing Day 2022. Credit: Facebook

Emma was stabbed in the heart, and despite attempts to save her with open-heart surgery on the front lawn, she died at the scene.

Lee suffered serious injuries but survived.

During sentencing, Justice Sullivan revealed confronting details including how the offender had attempted to stab both multiple times, and how the knife blade snapped due to the force used.

The court also heard the teen had a significant history of break-ins, but had never previously been jailed.

Legal experts say it could be months before a ruling is handed down.