The Court of Appeal reserved a decision on Wednesday on an appeal from a man jailed for the murder of an undercover police officer.
John Skinner shot Sergeant Don Wilkinson and his partner with an air rifle in South Auckland in 2008 after he discovered the officers on his property.
He was sentenced last year in the Auckland High Court to a minimum of 15 years' imprisonment.
He was also found guilty of attempting to kill the officer's partner, who has name suppression.
An appeal against an eight-year sentence for Mr Wilkinson's manslaughter by Skinner's associate, Iain Clegg, was dismissed in September.