Skinner watched by video link from Auckland today as his lawyer, Marie Dyhrberg, argued in the Court of Appeal at Wellington that there had been a miscarriage of justice.
The panel of three judges has reserved its decision.
Ms Dyhrberg said Skinner did not have murderous intent and fired in self defence from an air rifle he did not know was capable of killing someone.
"The Crown case was that he was a drug manufacturer protecting his operation,'' she said.
But it was unlikely her client would have "acted murderously'' over items found at his home, where no P lab was discovered.
Because Skinner had security lighting at the property it was highly prejudicial to say he was a drug manufacturer.
He had wanted to check out the intruders, who looked like burglars or criminals, and followed them in case they returned. The air rifle was fired when he thought Mr Wilkinson was reaching for a gun.
It was a reflex action carried out in fear of his own life, said Ms Dyhrberg, who submitted that the trial judge should have better directed the jury on self-defence and allowed them to consider provocation.
Crown lawyer Russell Collins told the court self defence was not credible and there was no evidence that Skinner had lost the power of self control - a necessary legal ingredient of provocation.
"This was an execution. There was point-blank use of a firearm with murderous intent,'' he said.
The minimum term of imprisonment handed down to Skinner could not be described as manifestly excessive.
In June last year a jury found Skinner guilty of the murder of Mr Wilkinson, the attempted murder of the second police officer and assault with a firearm.
Clegg, then 33, was acquitted of the Wilkinson murder but convicted of his manslaughter. He was found not guilty of the attempted murder of the second officer.
