The appeal of Quinton Winders, found guilty of murdering road worker George Taiaroa in 2013, had a contentious police interview at the centre of proceedings.
The day-long hearing of submissions took place in the Court of Appeal in Wellington on Tuesday.
Winders is appealing his conviction and sentence to at least 17 years in jail, handed down in 2016, for the murder of Mr Taiaroa, who was shot dead while carrying out stop-go duties at Atiamuri, near Tokoroa.
Winders was arrested following a police investigation which took more than two-and-a-half years.
He has always denied killing Mr Taiaroa.
The Crown said the killing was revenge for a minor accident involving Winders' father at another stop-go a week earlier.
In the Court of Appeal, Mr Morgan's key points in his submission to justices Asher, Clifford and Gilbert included that the propensity for Winders to use firearms was overstated at the trial; that a police interview - where Winders gave crucial background as to his movements around the time Mr Taiaroa was killed - should not have been included at the trial; that there was conflict between the foreman and two jurors; and that the murder was not as calculated as the judge decided in sentencing.
On the jury issue, Mr Morgan said two jurors approached the judge, saying the foreman was "bossy and unprepared to listen to the views of others".
"We're talking about a murder trial and for these jurors to raise this, it means there was discord among them that could ultimately affect a verdict."
Mr Morgan said the police interview should not have been admitted at the trial, as Winders was unaware he was a possible murder suspect.
Annabel Markham, for the Crown, however, said Winders was repeatedly reminded of his rights during the interview and reminded of the "real purpose" of his being talked to by police.
"It was crystal clear that they were interested in talking to the appellant [Winders], there was no confusion or miscarriage of justice and he continued to answer the officers' questions.
"He knew a man had been murdered and the police were looking for a Jeep Cherokee."
Regarding the sentence, Mr Morgan said it could be argued the decision to drive a long distance to shoot Mr Taiaroa was made "on the day", rather than it being a "calculated" decision.
The judges' decision was reserved.