Beverly Lawrie said during the sentencing of her son's killers today that the bottom had fallen out of her life the day her son was killed.
The man who shot Mr Wilkinson, John Ward Skinner, was handed a life sentence with a minimum non-parole period of 15 years by Justice Geoffrey Venning at the High Court in Auckland today.
Skinner had been found guilty in June of murdering Mr Wilkinson, along with the attempted murder of Mr Wilkinson's colleague, who has name suppression, and assault with a weapon.
Skinner's co-accused, Iain Lindsay Clegg, was jailed for eight years, with a minimum non-parole period of four years, for Mr Wilkinson's manslaughter.
Ms Lawrie said her son had worked in several dangerous places overseas and that he had come back to New Zealand because he thought it would be a safe place to live.
"The last place I expected him to be killed was in New Zealand."
Ms Lawrie said she thought Skinner and Clegg were cowards who showed no respect for human life.
"They had opportunity to turn away. They didn't have to chase Donny and his colleague down. They didn't have to shoot him. Skinner didn't have to kill my son. At any time both of them could have simply turned away and gone back."
Ms Lawrie said she was one of few people her son could speak to about his life as a covert operative and his everyday life as a member of a squash club and a sailing club.
"I was fortunate enough to hear of the heroic acts that he'd done," she said.
"He shared both lives with me and I was privileged for that."
Mr Wilkinson and his colleague had been trying to install a tracking device on a car at Skinner's house in Hain Ave, Mangere as part of a covert drugs operation when they were detected.
After they ran away, Skinner and Clegg got in a car to chase them. They found the two officers down a driveway, where both were shot by Skinner.
Mr Wilkinson, who was not wearing a protective vest, died at the scene.
His colleague, who was wearing protective clothing, survived.
Skinner had argued during the trial that he thought the two officers, who did not identify themselves, were burglars.
Crown prosecutor Simon Moore said Skinner should receive a minimum non-parole period of 14-17 years.
In reply to submissions that Skinner thought the two officers, who did not identify themselves, were burglars, Mr Moore said the shooting was a "wholly disproportionate reaction".
Skinner's lawyer Marie Dyhrberg said the shooting was a tragic incident and its enormity was not lost on Skinner.
She said the incident "could be described as showing a man who one night in the heat of the moment, engaged in out of character actions".
Clegg's lawyer Graeme Newell said his client was saddened at the incident and hoped for forgiveness from Mr Wilkinson's family.
He said Clegg was reacting to a situation where he thought two people were trying to access his car while his girlfriend was in it.
Justice Venning said he found Skinner's evidence during the trial "was unconvincing and not credible in a number of ways".
He said he rejected any suggestion there was any action from Mr Wilkinson which justified Skinner's claims of self-defence.
"Your actions were deliberate sustained actions carried out over a period of time," he said.
"You both knew and intended that when you caught up with them you would deal with them."
He said the fact they thought the two officers were intruders was not a mitigating factor.
"Even if they were you had no right to act in the way you did," he said.
"They left immediately that they were alerted to your presence. They were no further threat to you, your family or your property at that stage."
