A Dunedin cleaner found guilty of murdering his supervisor has had his appeal against the conviction dismissed.
Alexander Merritt, 20, was found guilty of the 2015 murder of Karin Ross, and sentenced to a minimum 12 years in prison.
Karin Ross was Alexander Merritt's supervisor at Spotless Cleaning in Dunedin, and had chastised him for repeatedly parking in a mobility carpark at his regular workplace, a polytech, and for his attitude and behaviour.
Merritt was to face a disciplinary hearing on 1 December but this was delayed.
In the early hours of 2 December Karin Ross was attacked with a tack hammer and killed by Merrit as she returned to the Spotless premises after a night of work.
The next morning Karin Ross' body was found by Merritt's mother, who also worked at Spotless.
The Court of Appeal judgement said Merritt has never accepted he killed Ms Ross, but that "in the face of powerful forensic and circumstantial evidence he does not challenge the jury verdict on that ground."
Merritt did appeal on the grounds that his trial counsel failed to pursue a diagnosis of Autism Spectrum Disorder (ASD) which was made shortly before the trial, and therefore lost the opportunity to pursue a defence that he lacked mens rea, or that his autism might have affected his capacity to form murderous intent.
He also said his lawyer should have fought admission of his video police interview, and that when he decided not to visit the crime scene with the jury he did not give informed consent.
In their findings the three appeal judges said there were three psychological reports on Merritt which did mention his capacity to form murderous intent, and indicated there was a strong indication of a ASD diagnosis.
Merritt's trial counsel Anne Stevens said she had discussed a defence of lack of mens rea with Merritt but he did not instruct her to pursue it.
The judgement said Merritt accepted evidence from Crown witnesses that he disliked Ms Ross, had wished her harm in the past, and did not mourn her death. The judgement said in light of this it was Anne Stevens' opinion that a mens rea defence would have been hopeless.
The video police interview took place on 4 December, and both defence and prosecution accept that Merritt chose not to exercise his right to a lawyer. In the interview he said he did not kill Karin Ross, but admitted indifference to her death. He also said that apparent injuries to his face scratches were self inflicted in his sleep.
The decision said the police interview did not amount to bullying or cross-examination.
Anne Stevens said Merritt was informed of his right to attend the crime scene with the jury when it visited, but a consensus was reached that there was little to be gained, and some risk, in that Merritt might convey his indifference to the jury. The court of appeal judgement said there was no evidence that Merritt not attending the crime scene affected the verdict.
The judges say they do not agree there was an error in Merritt's case, and dismissed the appeal.