ACT Court of Appeal extends Jaycsen Anthony Newby's sentence for murder of Frankie Prineas

Frankie Victor Prineas died after being stabbed 37 times by Jayscen Anthony Newby on January 11, 2020. (Supplied)

Convicted killer Jayscen Anthony Newby will spend at least five more years in jail after the ACT Court of Appeal found his original sentence was "manifestly inadequate".

Newby, 28, could be seen on a video link to Canberra's jail, pacing and banging on the door, as he waited for the judge to arrive in court this morning.

Newby was previously found guilty of the 2020 murder of Frankie Prineas, who had that evening been on a Tinder date with a woman with whom Newby had once had a relationship.

The court heard Newby had burst in on the pair while they were in bed in the woman's Charnwood home and stabbed Mr Prineas 37 times, including in the heart.

In June last year, Newby was sentenced to 20 years in jail with a non-parole period of 10 years.

At the time, Mr Prineas's family said the sentence was too short and that they were "stunned" by the outcome.

The original judge had described the scene as a "blood bath", saying Newby had not shown any remorse.

The Court of Appeal also noted the extreme violence of the crime in its reasons for extending Newby's sentence today, explaining how the pair did not even know each other.

"Mr Prineas had not done anything to provoke Newby," the appeal court said, noting that Mr Prineas had been "naked and defenceless".

Frankie Prineas died from "extensive" injuries after he was stabbed by Jayscen Anthony Newby at a property in Charnwood. (ABC News: Isaac Nowroozi)

Prosecutors had told the Court of Appeal that Newby had been given too much of a discount for his plea of guilty, and there was an insufficient explanation for the low non-parole period.

A key issue was whether the original judge should have recognised there was an overwhelming prosecution case and assessed the reduction for a guilty plea against that.

The Court of Appeal today backed the prosecution's argument.

"If it was not acceded to, there needed to be a clear and express explanation as to why the prosecution case was not found to be overwhelmingly strong, particularly given the circumstances of the matter."

The court allowed the prosecution case, and resentenced Newby to 24 years in jail, with a non-parole period of 15 years, meaning he will not be eligible for release until 2035.