Corey James “Budge” Martin, 40, was found guilty of fatally bashing 26-year-old Andre Le Dinh, a man almost half his size.

The bashing occurred in 2010, after Martin entered the victim’s secure apartment complex in Belconnen and knocked on his door.

Martin planned to steal cannabis and money from Mr Le Dinh, and he told others he would immediately set upon and subdue his victim.

Evidence suggested Martin planned to knock Mr Le Dinh out, and then knock him out again if he regained consciousness.

The brutal attack left blood spattered across the apartment, and the Crown alleged Martin walked out while Mr Le Dinh lay on the floor, choking and dying.

The vastly larger man claimed he was acting in self-defence, saying Mr Le Dinh had become aggressive and violent towards him. He said Mr Le Dinh had been alive and standing when he walked out.

Mr Le Dinh weighed 48 kilograms and stood just 165cm tall. Martin weighed 110 kilograms and is 189 centimetres.

The only injuries Martin sustained were to his hand, which he admitted were from punching his victim.

A Supreme Court jury rejected the killer's version in early 2013, finding him guilty of murder.

Martin has since appealed his conviction in the ACT Court of Appeal, and is still waiting on a judgment.

The convicted killer has now also appealed his sentence of 22 years, with a non-parole period of 17 years and six months, which was handed down by Acting Justice John Nield in October.

The hearing of that appeal took place on Monday.

Barrister Shane Gill told a full bench of the ACT Court of Appeal that the sentence did not fit in the “broad pattern” of past murder sentences.

Mr Gill argued that Justice Nield had made a number of findings of fact during sentencing, which were not supported by the evidence.

That included the suggestion that Martin had grabbed Mr Le Dinh’s head and smashed it on the floor, causing fractures to his skull.

The court heard there was evidence consistent with Martin doing such a thing, but that it had not been proven.

The fractures in the skull, Mr Gill argued, could also have been caused by an uncontrolled fall, possibly following a punch.

He said there was a concern that a greater callousness was found in sentencing than the evidence warranted, noting there were murders that could be described as the “least worst” of cases.

Mr Gill also argued the parole period was wrongly set.

In response, Crown prosecutor Margaret Jones said Martin’s appeal appeared to be pointing towards an argument that the sentence was manifestly excessive.

But Ms Jones said the “manifest excessiveness” argument had not actually been asserted by Martin as a ground in the appeal.

She said the errors in sentencing had not been made out by Martin’s lawyers.

The full bench of the Court of Appeal – consisting of Justice Richard Refshauge, Justice John Burns, and Justice Iain Ross – as reserved its decision.