Anthony Robert Moore (48) had pleaded guilty to unlawful possession of a firearm and perverting the course of justice and was jailed for three years and four months by Justice David Gendall in the High Court at Greymouth in October.
Despite being declared unfit to hold a firearms licence, Moore had two weapons and provided one to George Sean Warren who claimed he needed protection from a gang.
On October 22, driven by Corey Robert Towersey, Warren went to Hayley Jane Williams' home, angry about an indecent assault complaint she had made against him.
He shot her in the throat outside her home, killing her instantly, while her three children were inside the house.
In the weeks following the murder, Moore and Towersey conspired to hide their involvement and discussed threatening witnesses.
Despite the obfuscation, defence counsel Marcus Zintl told the Court of Appeal in Dunedin this week that Moore's jail term was excessive because the man's remorse had not been correctly assessed.
He acknowledged the appellant initially denied his role in the crime to police but stressed he later came clean.
Mr Zintl said his client also wrote a letter of apology and should have received a discount from his sentence.
Justice Graham Lang appeared sceptical.
''When did this remorse suddenly come in? He was busy going round threatening witnesses,'' he said.
''At what point did he become remorseful? Shortly before sentencing, I suspect.''
Mr Zintl said his client was also robbed of a chance to sit down with Mrs Williams' family for a restorative-justice conference, because no referral for such a meeting was made by the court.
But Justice Forrie Miller said that could only be given weight by the court if the victim's family had wanted such a meeting.
Otherwise the submission was ''purely speculative'', he said.
Mr Zintl conceded the family had considered meeting Moore but withdrew when they heard he was appealing his sentence.
Crown counsel Rebecca Thomson said two months of denials and attempts to suppress evidence did not suggest the appellant was remorseful.
Indeed, she said, he was lucky his period behind bars was not longer.
The judge had decided against increasing the sentence for Moore's criminal history which included another conviction for unlawfully possessing a firearm in 2004.
In June last year, Warren was jailed for life with a minimum non-parole period of 17 years, while Towersey got four years eight months for manslaughter at sentencing last week.
The court reserved its decision on Moore's appeal.
