Joshua Higgins, in his early 30s, was found guilty of manslaughter in early 2021 after stabbing his friend Jae-Ho Oh in March 2019 following hours of heavy drinking between the pair.

Higgins pleaded not guilty to murder but an ACT Supreme Court jury trial of 21 days found him guilty of the lesser charge.

He was sentenced last August to eight and a half years jail with a non-parole period of five years and three months.

The court heard Higgins, 30 at the time, asked Mr Oh, 56, if he could stay over after his mother told him not to return because he lost money while gambling in NSW.

Before going over, Higgins consumed the drug ice and had not slept for about 60 hours.

On March 10, the pair spent the day drinking at Mr Oh's Gungahlin townhouse where Higgins, a former hospitality worker, had 20-30 standard drinks before going to bed.

Higgins alleged he was then woken by Mr Oh sexually assaulting him.

He said Mr Oh then started yelling before grabbing two knives on separate occasions, leading to violent struggles before the killing.

The victim sustained 34 separate injuries that included stabs penetrating his chest wall and his lungs, as well as neck, face and back.

Higgins was then seen - with a bloodstained shirt and knife - running on the streets screaming for help before police arrived.

In a previous court session, Crown prosecutor Trent Hickey described the killing as an "extremely excessive" and a "short-and-frenzied attack" in which the victim "looked dead" before emergency services arrived.

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Kieran Ginges, lawyer for Higgins, appealed the sentence based on three grounds: two errors related to the Crimes Sentencing Act and a generalised allegation of manifest excess.

The first ground was that the sentencing judge, Justice John Burns, failed to impose a lesser sentence because Higgins helped the administration of justice by ensuring the trial was run efficiently.

It was argued that while the judge applied a 15 per cent discount for Higgins' offer to plead guilty to manslaughter, which the Crown rejected, he failed to apply further discount for the way the trial was run if he did intend to apply one.

Mr Ginges also argued that the discount for the offender's offer to plead guilty was lower than reasonably appropriate in all the circumstances.

The second ground was that the case warranted a substantial reduction in moral culpability, because of Higgins' mental health, and in general deterrence.

It was also contended that the sentencing judge failed to acknowledge the impact that full-time jail would have on Higgins' PTSD and that an extended parole period would best address his PTSD and substance abuse.

As for the final ground, it was contended that the total effective sentence is manifestly excessive when considering it against the circumstances in which the offence occurred, the judge's assessment of mid-level objective seriousness and the subjective circumstances of Higgins calling for significant leniency.

In a decision on Tuesday, Justices David Mossop, Chrissa Loukas-Karlsson and Michael Lee of the ACT Court of Appeal dismissed all grounds.

The court said the extent of help with the administration of justice "was not present here" and that the 15 per cent discount was "clearly within the range of discounts open and no error is evident".

"This is not a case where the sentencing judge failed to consider the appellant's mental health conditions," the court said.

"His Honour accepted there should be 'some' reduction in the appellant's moral culpability and that general deterrence should be moderated on account of his diagnosis of PTSD."

In relation to it being manifestly excessive, the court said the sentencing judge's approach "was orthodox and unexceptionable".

"The result does not suggest manifest error," it said.

"Indeed, in the light of the objective seriousness of the offence and the appellant's subjective circumstances, the sentence imposed was well within the appropriate range of sentences open to the sentencing judge."

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